Organotin oxide hydroxide patterning compositions, precursors, and patterning

ABSTRACT

Organometallic precursors are described for the formation of high resolution lithography patterning coatings based on metal oxide hydroxide chemistry. The precursor compositions generally comprise ligands readily hydrolysable by water vapor or other OH source composition under modest conditions. The organometallic precursors generally comprise a radiation sensitive organo ligand to tin that can result in a coating that can be effective for high resolution patterning at relatively low radiation doses and is particularly useful for EUV patterning. The precursors compositions are readily processable under commercially suitable conditions. Solution phase processing with in situ hydrolysis or vapor based deposition can be used to form the coatings.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of copending U.S. patent applicationSer. No. 16/987,120 filed Aug. 6, 2020 to Meyers et al., entitled“Organotin Oxide Hydroxide Patterning Compositions, Precursors, andPatterning,” which claims priority to U.S. patent application Ser. No.16/238,779 filed Jan. 3, 2019, now U.S. Pat. No. 10,775,696, to Meyerset al., entitled “Organotin Oxide Hydroxide Patterning Compositions,Precursors, and Patterning,” which claims priority to U.S. patentapplication Ser. No. 15/291,738, filed Oct. 12, 2016, now U.S. Pat. No.10,228,618, to Meyers et al., entitled “Organotin Oxide HydroxidePatterning Compositions, Precursors, and Patterning,” which claimspriority to U.S. provisional patent application 62/240,812 filed Oct.13, 2015 to Meyers et al., entitled “Organotin Oxide HydroxidePatterning Compositions With Precursor Vapor Deposition,” and to U.S.provisional patent application 62/297,540 filed Feb. 19, 2016 toCardineau et al., entitled “Precursor Compositions for Organotin OxideHydroxide Photoresist Films,” all of which are incorporated herein byreference.

FIELD OF THE INVENTION

The invention relates to precursor compositions that can be coated andin situ hydrolysed to form coatings comprising organotin oxidehydroxide. The invention further relates to radiation sensitiveorganotin oxide hydroxide coatings that can be patterned effectivelywith UV light, EUV light or electron-beam radiation to form highresolution patterns with low line width roughness.

BACKGROUND OF THE INVENTION

For the formation of semiconductor-based devices as well as otherelectronic devices or other complex fine structures, materials aregenerally patterned to integrate the structure. Thus, the structures aregenerally formed through an iterative process of sequential depositionand etching steps through which a pattern is formed of the variousmaterials. In this way, a large number of devices can be formed into asmall area. Some advances in the art can involve that reduction of thefootprint for devices, which can be desirable to enhance performance.

Organic compositions can be used as radiation patterned resists so thata radiation pattern is used to alter the chemical structure of theorganic compositions corresponding with the pattern. For example,processes for the patterning of semiconductor wafers can entaillithographic transfer of a desired image from a thin film of organicradiation-sensitive material. The patterning of the resist generallyinvolves several steps including exposing the resist to a selectedenergy source, such as through a mask, to record a latent image and thendeveloping and removing selected regions of the resist. For apositive-tone resist, the exposed regions are transformed to make suchregions selectively removable, while for a negative-tone resist, theunexposed regions are more readily removable.

Generally, the pattern can be developed with radiation, a reactive gas,or liquid solution to remove the selectively sensitive portion of theresist while the other portions of the resist act as a protectiveetch-resistant layer. Liquid developers can be particularly effectivefor developing the latent image. The substrate can be selectively etchedthrough the windows or gaps in the remaining areas of the protectiveresist layer. Alternatively, materials can be deposited into the exposedregions of the underlying substrate through the developed windows orgaps in the remaining areas of the protective resist layer. Ultimately,the protective resist layer is removed. The process can be repeated toform additional layers of patterned material. The materials can bedeposited using chemical vapor deposition, physical vapor deposition orother desired approaches. Additional processing steps can be used, suchas the deposition of conductive materials or implantation of dopants. Inthe fields of micro- and nanofabrication, feature sizes in integratedcircuits have become very small to achieve high-integration densitiesand improve circuit function.

SUMMARY OF THE INVENTION

In a first aspect, the invention pertains to a coating solutioncomprising an organic solvent, a first organometallic composition, and ametal compound with hydrolysable ligand-metal bonds. In someembodiments, the first organometallic composition can be represented bythe formula R_(z)SnO_((2-(z/2)-(x/2)))(OH)_(x) where 0<z≤2 and0<(z+x)≤4, by the formula R_(n)SnX_(4-n), where n=1 or 2, or a mixturethereof, in which R is a hydrocarbyl group with 1-31 carbon atoms, and Xis a ligand with a hydrolysable M-X bond. The hydrolysable metalcompound can be represented by the formula MX′_(n), where M is a metalchosen from groups 2-16 of the periodic table of elements, X′ is aligand with a hydrolysable M-X′ bond or a combination thereof, and n isdetermined by the valency of the metal and the ligand charge.

In a further aspect, the invention pertains to a coating solutioncomprising an organic solvent, at least about 10 mole percent relativeto total metal content of a first organometallic composition, and atleast 10 mole percent relative to total metal content of a secondorganometallic composition. In some embodiments, the firstorganometallic composition can be represented by the formulaR_(z)SnO_((2-(z/2)-(x/2)))(OH)_(x), where 0<z≤2 and 0<(z+x)≤4, by theformula R_(n)SnX_(4-n) where n=1 or 2, or a mixture thereof, in which Ris a hydrocarbyl group, and Sn—X is a hydrolysable chemical bond. Thesecond organometallic composition can be represented by the formula R⁺_(y)SnX′_(4-y) where y=1 or 2, in which R′ is a hydrocarbyl group thatis different from R, and X′ is a ligand having a hydrolysable Sn—X′ bondthat is the same or different from X.

In another aspect, the invention pertains to a method for forming aradiation patternable coating, the method comprising exposing aprecursor coating on a substrate to water vapor, in which the precursorcoating comprises a first organometallic composition, and a secondhydrolysable composition. The first organometallic composition can berepresented by the formula R_(z)SnO_((2-(z/2)-(x/2))(OH)_(x) where 0<z≤2and 0<(z+x)≤4, or R′_(n)SnX_(4-n) where n=1 or 2 and R and R′ areindependently hydrocarbyl groups with 1-31 carbon atoms. The secondhydrolysable composition can be either a second organometalliccomposition represented by the formula R″_(y)SnX′_(4-y) where y=1 or 2and R″ is different from R′ and X′ is a ligand with a hydrolysable Sn—X′bond that is the same or different from X, or an inorganic compositionML_(v), where v is 2≤v≤6 and L is a ligand with a hydrolysable M-L bondthat is the same or different from X and X′. In some embodiments, theexposing step results in hydrolysis of the precursor coating compoundsto form a coating comprising ((R orR′)_(a)R″_(b))SnO_((2-((a+b)/2)-(w/2)))(OH)_(w), where 0<(a+b)≤2 and0<(a+b+w)<4; or comprising y ((R orR′)_(a)R″_(b))SnO_((2-((a+b)/2)-(w/2)))(OH)_(w)·zMO_(((m/2)-1/2))(OH)_(l) where 0<(a+b)≤2, 0<(a+b+w)<4, m=formal valenceof M^(m+), 0≤1≤m, y/z=(0.05 to 0.6), and M=M′ or Sn, where M′ is anon-tin metal of groups 2-16 of the periodic table.

In additional aspects, the invention pertains to a method for forming aradiation patternable coating comprising a metal oxo-hydroxo networkwith metal cations having organic ligands with metal carbon bonds andmetal oxygen bonds, the method comprising inputting into a depositionchamber closed from the ambient atmosphere separately a first precursorvapor comprising a compound R_(n)SnX_(4-n) where n=1 or 2, wherein R isa hydrocarbyl group with 1-31 carbon atoms, and X is a hydrolysable oroxidizable ligand and a second precursor vapor comprising an oxygencontaining compound capable of hydrolyzing or oxidizing the firstprecursor vapor under conditions in the deposition chamber to form ahydrolyzed or oxidized composition. Generally, a substrate can beconfigured with a surface to receive the hydrolyzed or oxidizedcomposition.

In other aspects, the invention pertains to a coated substratecomprising a substrate with a surface and a coating on the surfacecomprising an organometallic composition represented by the y(R_(z)SnO_((2-(z/2)-(w/2)))(OH)_(w).z MO_((m/2)-1/2))(OH)_(l) where0<z≤2, 0<(z+w)≤4, m=formal valence of M^(m+), 0≤1≤m, y/z=(0.05 to 0.6),and M=M′ or Sn, where M′ is a non-tin metal of groups 2-16 of theperiodic table, and R is hydrocarbyl groups with 1-31 carbon atoms.

Furthermore, the invention pertains to a substrate and a radiationsensitive coating comprising an alkyl metal oxide hydroxide having adose-to-gel (D_(g)) of no more than about 6.125 mJ/cm².

Moreover, the invention pertains to a substrate comprising an inorganicsemiconductor layer and a radiation sensitive coating material along asurface. In some embodiments, the radiation coating material can bepatterned with EUV light at a wavelength of 13.5 nm in a pattern of16-nm lines on a 32-nm pitch to achieve a critical dimension of 16 nmwith a dose from about 8 mJ/cm2 to about 25 mJ/cm2 with a line widthroughness of no more than about 4 nm. The radiation sensitive coatingmaterial can comprise metal, such as Sn, and can comprise at least 5weight percent metal and in other embodiments at least about 20 weightpercent metal.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic perspective view of a radiation patternedstructure with a latent image.

FIG. 2 is a side plan view of the structure of FIG. 1.

FIG. 3 is a schematic perspective view of the structure of FIG. 1 afterdevelopment of the latent image to remove un-irradiated coating materialto form a patterned structure.

FIG. 4 is a side view of the patterned structure of FIG. 3.

FIG. 5 is a schematic perspective view of the structure of FIG. 1 afterdevelopment of the latent image to remove irradiated coating material toform a patterned structure.

FIG. 6 is a side view of the patterned structure of FIG. 5.

FIG. 7 is a scanning electron (SEM) micrograph of a regular patternformed on substrate with a line spacing of 16.7 nm formed with an EUVdose of 56 mJ/cm².

FIG. 8 is a plot of film thickness following exposure and development asa function of EUV dose formed for 50 circular pads 500 microns indiameter exposed with stepped doses for substrates coated with radiationresists as described herein with in situ hydrolysis.

FIG. 9 is a plot with two FTIR spectra comparing films formed withsolution based hydrolysis versus in situ hydrolysis in the coating.

FIG. 10 is a set of plots with EUV contrast curves involving a functionof dose for coatings formed with three different amounts of Sn(NMe₂)₄ inthe radiation sensitive coating prior to in situ hydrolysis.

FIG. 11 is a set of SEM micrographs for five patterned coatings formedwith indicated compositions and irradiation doses.

FIG. 12 is a plot of line width roughness (LWR) as a function ofdose-to-size for 6 resist compositions based on patterned with EUV lightat a wavelength of 13.5 nm in a pattern of 16-nm lines on a 32-nm pitchwith the dose-to-size value to achieve a critical dimension of 16 nm.

FIG. 13 is a set of plot of EUV contrast curves involving a function ofdose for 5 coatings formed with varying amounts of methyl ligands as aradiation sensitive group.

FIG. 14 is a set of plots of space critical dimensions as a function ofirradiation dose for coatings with three different amounts of methylligands.

FIG. 15 is set of three SEM micrographs for patterns formed withdiffering EUV radiation doses.

FIG. 16 is a schematic of an apparatus for the formation of an organotinoxide hydroxide layer on a substrate.

DETAILED DESCRIPTION OF THE INVENTION

Improved patterning performance at lower radiation doses can be obtainedusing organotin patterning compositions with a selected ratio ofradiation sensitive alkyl-Sn bonds and/or a selected amount of tinprecursors free of radiation sensitive ligands, and improved processingof the radiation patternable coatings can be achieved using in situsolvolysis, e.g., hydrolysis, of the precursor compositions. Theradiation patternable coatings generally compriseR_(z)SnO_((2-(z/2)-(x/2)))(OH)_(x) compositions, where 0<z≤2 and0<(z+x)<4, and R is a radiation sensitive alkyl ligand, which in someembodiments can exhibit improved low-dose radiation patterning whenformed with a selected amount of SnX₄ precursor compounds to modify thevalue of z for the overall composition. The use of in situ hydrolysisallows for the effective use of precursor compositions through solutionbased processing that would be difficult or impossible to achievethrough the direct dissolution and deposition of alkyl tin oxo-hydroxocompositions. As described herein, processing is improved through insitu solvolysis to form the patternableR_(z)SnO_((2-(z/2)-(x/2)))(OH)_(x) compositions. Vapor deposition can beuseful for the deposition of certain precursor coatings as analternative to solution based processing to form the organotin oxidehydroxide precursors. The patterning compositions are particularlyuseful for EUV patterning at reduced doses, and low line width roughnesscan be obtained for small features.

Organotin oxide hydroxides with the general formulaR_(z)SnO_((2-(z/2)-(x/2)))(OH)_(x) where 0<(x+z)<4 and z>0 have beenfound to offer excellent performance as patterning materials, commonlyknown as photoresists, when deposited as thin coatings and exposed withUltraviolet (UV), Extreme Ultraviolet (EUV), or electron-beam radiationand developed with appropriate solvents. Previous work has shown thatorganotin oxide hydroxides can provide a basis for the formation ofstable precursor solutions that can form resist layers providing goodradiation absorption and development rate contrast. The organotincompositions are effectively used as negative resists or positiveresists. The efficacy of these compounds for EUV and electron-beamresists is described in U.S. Pat. No. 9,310,684 B2 to Meyers et al.,entitled “Organometallic Solution Based High Resolution PatterningCompositions,” incorporated herein by reference. Based on the currentsynthesis approaches, it seems appropriate to extend these compounds toextend to the value of (x+z)=4 so that 0<(x+z)≤4 Improved patterningperformance found with branched alkyl ligands and blends of alkyl tinoxide hydroxide compositions is described in published U.S. patentapplication 2016/0116839 A1 to Meyers et al. (hereinafter the '839application), entitled “Organometallic Solution Based High ResolutionPatterning Compositions and Corresponding Methods” incorporated hereinby reference.

The foregoing references describe organotin oxide hydroxide photoresistfilm deposition by coating precursor solutions containingR_(z)SnO_((2-(z/2)-(x/2)))(OH)_(x) compositions prepared bypre-hydrolysis of one or more R_(n)SnX_((4-x)) compositions where (n=1or 2), isolation and purification of the organotin hydrolysate(s), anddissolution of the oxide hydroxide(s) in a suitable solvent or mixturethereof. However, the dissolution and coating of pre-hydrolysedorganotin oxide hydroxides may have substantial constraints on theaccessible ligand identities and stoichiometries mandated by theavoidance of poor solubility of one or more hydrolysates, as well ascomplex hydrolysis processes for some embodiments which have thepotential to introduce undesirable contaminates. Moreover, even ifsoluble resist precursor solutions can be prepared of the organotinoxide hydroxide precursor compositions, undesirable solvents may berequired, or film morphology may be impaired.

It has been discovered that many of these constraints may be overcome bythe preparation of resist precursor solutions consisting of one or moresuitable R_(n)SnX_((4-n)) compounds dissolved in an appropriate solventor mixture of solvents, where X is a ligand with a hydrolysable Sn—Xbond. If the precursor R_(n)SnX_((4-n)) is sufficiently reactive withwater vapor, it can undergo in situ -M-X hydrolysis and condensation inthe presence of water to produce the corresponding oxide hydroxide asillustrated in the following general reactions:

R_(n)SnX_(x) +xH₂O→R_(n)Sn(OH)_(x) +xHX

R_(n)Sn(OH)_(x)→R_(n)SnO_((2-(n/2)-(x/2)))OH_(x)+(x/2)H₂O

where (0<(x+z)≤4). Thus, by the use of coating solutions comprising theR_(n)SnX_((4-n)) compounds, a greater range ofR_(z)SnO_((2-(z/2)-(x/2)))(OH)_(x) compositions can be formed inpractical procedures as photoresist coatings. In these methods the R—Snmoiety is at least partially preserved through the hydrolysis andcondensation process, and the resulting film has both M-C and M-O bonds.

In one embodiment of an in situ hydrolysis process, a precursorR_(n)SnX_((4-n)) is dissolved in a solvent, directly coated on asubstrate, optionally in the presence of water vapor (such as moistair), to produce a coating, and then additionally or alternatively bakedfurther in the presence of water vapor to form the organotin oxidehydroxide coating. Thus, water vapor for hydrolysis can be presentduring coating deposition and/or during a pre-patterning bake step toperform the in situ hydrolysis. Additionally, by blending multipleR_(n)SnX_((4-n)) compounds where n=0, 1, or 2 (such as SnX₄, RSnX′₃,R′SnX″₃ and R″₂SnX₂, where R, R′, and R″ are the same or different andX, X′, and X″ are the same or different) in a suitable solvent anR_(z)SnO_((2-(z/2)-(x/2)))(OH)_(x) (s) film of selected stoichiometry inthe range 0<z≤2 and 0<(x+z)≤4 may be readily deposited. Similarly,mixed-ligand hydrolysates comprising a mixture of an organotin oxidehydroxide R_(z)SnO_((2-(z/2)-(x/2)))(OH)_(x) (where 0<(x+z)<4 and z>0)with one or more different organotin oxidesR′_(b)SnO_((2-(b/2)-(a/2)))(OH)_(a) (where 0<(a+b)<4 and b>0) and whereR′≠R can be similarly prepared by this method. HydrolysableR_(n)SnX_((4-n) and) R′_(b)SnX_((4-b)) compounds can be dissolved in acommon solvent or mixture of solvents and spin-coated on a substrate forin situ hydrolysis. In both cases the high solubility and rapidhydrolyses of suitable molecular organotin precursor compoundsadvantageously sidesteps potential solubility restrictions of the targetorganotin oxide hydroxide hydrolysates and eliminates the need forcomplicated and sensitive synthetic procedures to isolate hydrolyzed andpartially condensed resist precursors ex situ. In this manner resistprecursor preparation can be significantly simplified and desirablecompositions with improved performance are enabled.

In another embodiment, the relatively high vapor pressures andreactivity of many molecular R_(n)SnX_((4-n)) compounds enable the useof vapor deposition methods for deposition of organotin oxide hydroxidethin-film photoresists. Potential deposition methods include, forexample, physical vapor deposition (PVD), chemical vapor deposition(CVD), atomic layer deposition (ALD), or modifications thereof. Forexample, one or more gaseous R_(n)SnX_((4-n)) compounds can beintroduced to a reaction chamber and reacted with a co-precursor such asH₂O or its associated decomposition products, either in the gas phase oron a substrates surface, thereby producing a radiation sensitiveorganotin oxide hydroxide coating. If the hydrolysable compound isdeposited on the surface with a subsequent hydrolysis reaction, thisprocess can be considered a PVD deposition with in situ hydrolysis, butif the hydrolysis takes place during a continuous deposition process, itcan be considered a CVD process. Likewise, if the hydrolysable precursoris sequentially adsorbed, chemisorbed, or decomposed on the substratesurface, and the residual film reacted with a second reactive precursorthrough multiple deposition/reaction cycles to deposit the correspondingorganotin oxide hydroxide it can considered an ALD process. Advantagesof vapor deposition methods may include reduced resist film defectdensity, improved thickness and compositional uniformity, as well asconformal and side-wall coating of substrate topography.

Organotin oxide hydroxide photoresist performance, including for exampleimaging dose, ultimate resolution, and line-width roughness (LWR), hasbeen found to be dependent upon the composition of the photoresistcoating. For these photoresist films with the compositionR_(z)SnO_((2-(z/2)-(x/2)))(OH)_(x) where 0<(x+z)≤4 and z>0, both theidentity of the radiation sensitive ligand R, as well as the R:Snstoichiometry represented by z are significant variables. Generally, thephoto resist film can comprise sufficient radiation sensitive ligands Rsuch that the thin film has a molar concentration ratio of radiationsensitive ligands to metal cations (z) from about 0.1 to about 2.Organotin oxide hydroxide resist films with ligand ratios in this rangemay be prepared by pre-hydrolysis of multiple R_(n)SnX_((4-n))precursors with z=1 or 2 in the appropriate stoichiometry, anddissolution of the resulting hydrolysates in a coating solvent, subjectto solubility and stability constraints. Certain stoichiometries,particularly those with 0.1<z<1, the photoresist compositions have beenfound to exhibit advantageous photoresist properties. However, forphotoresist compositions with z<1, the aforementioned processingconstraints may be onerous as the solubility of inorganicSnO_((2-(x/2)))(OH)_(x) hydrolysates (z=0) is typically extremely low inorganic solvents, outside of very limited conditions favoringco-hydrolysis and cluster condensation with specific organotin RSnX₃ orR₂SnX₂ moieties. Moreover, even when such conditions have beenidentified and hydrolysates isolated and dissolved, the precursorsolution stability, stoichiometry, ligand identity, and solvent may bedetrimentally limited relative to desirable values for operation as anEUV photoresist.

These processing and composition constraints can be overcome by addingreadily hydrolysable SnX₄ compounds directly to precursor coatingsolutions containing one or more pre-hydrolysed organotin oxidehydroxides, or one or more RSnX₃ and/or R₂SnX₂ compounds chosen toundergo substantially complete hydrolysis and subsequent condensationalong with HX by-product volatization on coating and baking in thepresence of water, or another suitable source of oxygen and hydrogen. Inthis way both the identity and relative stoichiometry of multipleradiation sensitive ligands in both the precursor coating solution andphotoresist film may be independently controlled across a wide range oftotal ligand to metal cation ratios, with relaxed solution stability andsolubility constraints and simplified precursor synthesis. Thus,appropriately selected SnX₄ compositions may be incorporated intoprecursor mixtures or processes to enable organotin oxide hydroxidevapor deposition with comparable compositions.

By relaxing the stability and solubility constraints inherent toorganometallic compounds with both M-C and M-O bonds, alternate metalspecies may also be added to the precursor coating solution or reactivegas mixture in the form MX′_(n) where M is a metal cation chosen fromgroup 2-16 metals, and n is determined by the valency of the metalcation and ligand charge, but is generally 3-6. When M≠Sn, the X′ ligandmay be the same or different as X in R_(n)SnX_((4-n)) compounds used inthe same formulation. In both cases these ligands and MX′_(n) aresubject to similar criteria; rapid and substantially complete hydrolysisin the presence of H₂O and diffusion and volatilization of X (X′) ligandhydrolysis products from the oxide hydroxide film. Alternate metalcations incorporated into the organotin oxide hydroxide coating in thismanner may be advantageous for tuning radiation absorption, filmdensity, metal-ligand thermolysis, development rate in preferreddevelopers, or other desired photoresist properties.

The identity and relative stoichiometry of multiple R—Sn moietiespresent in an organotin oxide hydroxide resist film have been previouslyfound to offer improved patterning performance as described in the '839application. While the branched alkyl ligands and associated blendedcompositions described therein are accessible at least in part usingpre-hydrolysed organotin oxide hydroxide compounds dissolved insolvents, significant constraints with respect to ligand identity andstoichiometry have been found in the context of practical processingsuitable for commercial use. Many of these constraints are associatedwith hydrolysate solubility. While some mono-organotin hydrolysates suchas n-butyltin oxide hydroxide have excellent solubility in a wide rangeof organic solvents, hydrolysates of mono-tert-butyl tin moieties, e.g.^(t)BuSnO_((3/2-(x/2)))(OH)_(x) where (0<x<3) are often insufficientlysoluble in useful solvents and/or desired solution concentrations aredifficult to reproduce and/or control. As demonstrated in the '839application, while it is possible to prepare a solution of^(t)BuSnO_((3/2-(x/2)))(OH)_(x) with methanol and solvent blends derivedtherefrom, the volatility, flashpoint, and toxicity of methanol renderit an undesirable solvent for use in semiconductor manufacturing.Moreover, the low maximum concentration limits the range of filmthicknesses accessible, and the compositions of blend precursorformulations and coatings possible. These constraints are obviated in anexample below, where high-performance ^(t)BuSnO_((3/2-(x/2)))(OH)_(x)photoresist films are demonstrated via spin coating of a solution of^(t)BuSn(NEt₂)₃ in 4-methyl-2-pentanol in the presence of water vapor.

Similarly, the low solubility of hydrolysates, e.g.MeSnO_((2-(z/2)-(x/2)))(OH)_(x), of mono-methyl tin moieties limits filmthickness and composition ranges of formulations and coatings. However,by preparing resist precursor solutions that comprise readilyhydrolysable and highly soluble MeSnX₃ compounds resist films comprisingthe resulting methyl-tin oxide hydroxide in blended formulations with^(t)BuSnO_((3/2-(x/2)))(OH)_(x) have been deposited and found to offeradvantageous lithographic performance. Significantly, using the methodsand precursor solutions disclosed herein, resist precursor solutionsolvent restrictions are substantially relaxed, and resist filmstoichiometry can be more readily adjusted to achieve usefullithographic properties. Desirable photoresist precursor solution andsubsequent film compositions comprising a mixture of organotin moietieswith different organic ligands (R, R′, R″, etc.) in a wide range ofmolar ratios with respect to each other and the metal cation are thusaccessible by mixing multiple hydrolysable organotin compoundsR_(n)SnX_((4-n))+R′_(z)SnX′_((4-z))+R″_(a)SnX″_((4-a))+ . . . (where0≤(n, z, a)≤2 and at least one of n, z, a, etc. >0).

Alternatively, selected R_(n)SnX_((4-n)) compounds where n=0, 1, or 2may be added to a precursor coating solution containing one or moreseparately synthesized organotin oxide hydroxide hydrolysates dissolvedin an appropriate solvent. Thus, the added R_(n)SnX_((4-n)) compoundscan hydrolyse on exposure to water vapor or hydroxide moieties,condensing with the initial organotin oxide hydroxides during coatingand baking steps to form a coating with an alkyl ligand to metal ratiodetermined by the stoichiometry of the precursor compounds originally inthe precursor coating solution.

The choice of ligand (X) with a hydrolysable Sn—X bond in theaforementioned compounds is significant for the efficacy of solvation,coating, and successful in situ hydrolysis. Appropriate ligands shouldform a stable bond with Sn in the absence of Lewis acids and generallybe strong nucleophiles that rapidly react with acidic protons to producespecies which readily desorb or volatilize from the condensing oxidehydroxide film, thereby reducing voids, domain segregation, or otherinhomogeneities. For R_(n)SnX_((4-n)) compounds, X may be a singleunique ligand, however, in certain embodiments, it may refer to acombination of multiple different ligands, e.g. R_(n)SnX¹ _(a)X² _(b)X³_(c)X⁴ _(d) where a+b+c+d−n=4, and 0≤n≤2. Examples of compounds of thistype are ^(t)BuSn(NEt₂)₂(O^(t)Bu), ^(t)BuSn(NEt₂)(NH₂)(O^(t)Bu),^(t)BuSn(NEt₂)(O^(t)Bu)₂, MeSn(NEt₂)(O^(t)Bu)₂, MeSn(NEt₂)₂(O^(t)Bu),(^(t)Bu)₂Sn(NEt₂)(O^(t)Bu), Me₂Sn(NEt₂)(O^(t)Bu), (Me)(^(t)Bu)Sn(NEt₂)₂,(Me)(^(t)Bu)Sn(NEt₂)(O^(t)Bu), (^(i)Pr)(^(t)Bu)Sn(NMe₂)(O^(t)Bu) andmixtures thereof.

The choice of —X ligand(s) may be determined in part by the identity ofthe hydrocarbyl ligand R, other hydrolysable ligands, and thestoichiometric ratio, R:Sn, as the reactivity of a given Sn—X moietywith respect to hydrolysis or solvolysis will be modified by the totalligand environment around the metal, both in terms of steric (kinetic)and the electrostatic (thermodynamic) effects.

Formulations comprising one or more R_(n)SnX_((4-n)) compound where —Xis a short-chain aliphatic dialkylamide —NR′₂ or alkoxide —OR′ ligandand where R′ contains <10 carbon atoms have been found to beparticularly suitable for these applications. When exposed toatmospheric moisture during the coating and baking processes, thesematerials rapidly hydrolyse and condense with other organotin precursorconstituents as described above, releasing volatile dialkylamines andalcohols and forming organotin oxide hydroxides with excellentphotoresist performance. Other useful ligands of this type include,amido, alkylamido, dialkylamido, alkoxo, aryloxo, azido, imido andothers known to those skilled in the art.

In some embodiments, such as the dissolution of an organotindialkylamide in a protic solvent such as an alcohol, the tin precursorcompound may react with the solvent. Through solvolysis, such asalcoholysis when the solvent is an alcohol, or similar reactions, fullor partial ligand metathesis may occur as illustrated in the reactionbelow.

R_(n)Sn(NR′₂)_((4-n))+(4-n)R″OH→R_(n)Sn(OR″)_((4-n))+(4-n)HNR′₂.  (2)

Such solvolysis and metathesis reactions in equation 2 are anticipatedand acceptable as well as potentially even beneficial provided theproduct tin species (such as a tin (IV) alkoxide, R_(n)Sn(OR″)_((4-n)))has the necessary attributes with respect to water reactivity,hydrolysis byproduct volatility, diffusivity, and other attributesdiscussed herein to produce an appropriate oxide hydroxide film uponcoating and baking in an appropriately humid environment.

The improved precursors described herein open up more possibilities forcompositions of patternable coatings based on reasonable coatingsolutions and in situ hydrolysis. In situ hydrolysis provides thecapability for a range of vapor phase deposition approaches asappropriate alternatives to solution based processing. Through theability to adjust the composition of patternable coatings with radiationsensitive ligands, improved patterning with lower radiation doses andgood pattern quality has been achieved.

Precursor Compositions

The precursor compositions for forming the resist coatings generallycomprise tin cations with appropriate radiation sensitive hydrocarbylstabilizing ligands and additional ligands with a hydrolysable bond toSn selected for processing. For processing into a patternable coating,the precursor compositions are generally formed into a solution with asolvent, generally an organic solvent that can be formed into a coatingthrough solution coating or a vapor based deposition process. Theultimate resist coatings are based on metal oxide chemistry, and theprecursor solutions of tin cations with alkyl ligands provide stablesolutions with good resist properties. The ligands of the precursorsolutions are generally selected to facilitate solution formation andrelated processing functions. As noted above, precursor compositionswith a ligand having a hydrolysable bond with Sn can be introduced intothe precursor solutions to improve the range of compositions that can beformed into stable solutions with the expectation that subsequenthydrolysis can provide for patternable coatings with organotin oxidehydroxide materials. Compositions with blends of alkyl ligands,generally with at least one branched alkyl ligand, have been found toprovide desirable patterning properties.

The alkyl ligands provide the radiation sensitivity, and the particularselection of ligands and stoichiometry relative to the metal caninfluence the radiation sensitivity. Also, the precursor solutions canbe designed to achieve desired levels of radiation absorption for aselected radiation energy based on the selection of the metal cations aswell as the associated ligands. While the discussion above outlines insignificant detail the ranges of precursor compositions suitable for theimproved processing described herein, more details are presented on theuse of alkyltin amido/alkoxy precursor compositions for in situhydrolysis. As noted above, various compounds are described that canprovide improved solubility in desirable solvents with goodprocessability into radiation sensitive coatings. A wide range ofprecursor engineering is made possible through the new classes ofprecursors involving at least some in situ hydrolysis with some vaporhydrolysis/oxidizing reactants, to form the radiation patternablecoatings.

In general, precursor solutions can comprise:

a1R¹ _(z1)SnO_((3/2-z1/2-x1/2))(OH)_(x1) +a2R²_(z2)SnO_((3/2-z2/2-x2/2))(OH)_(x2) + . . . +b1R¹′_(y1)SnX¹ _(4-y1)+b2R^(2′) _(y2)SnX² _(4-y2) + . . . +c1SnX^(1′) ₄ +c2SnX²′₄ + . . .+d1M¹X¹″_(n1) ,d2M²X²″_(n2)+ . . . ,  (1)

where a1+a2+ . . . +b1+b2+ . . . +c1+c2+ . . . +d1+d2+ . . . =1, i.e.,these parameters correspond with mole fractions of metal in theprecursor compositions in the solution, (0≤(a1, a2, . . . )≤0.99),(0≤(b1, b2, . . . )≤1), (0≤(c1, c2, . . . )<0.6), (0≤(d1, d2, . . .)≤0.5) with 0.01<(b1+b2+ . . . +c1+c2+ . . . ), R (R¹, R², . . . ) andR′ (R^(1′), R^(2′), . . . ) are independently hydrocarbyl groups or acombination thereof, X (X¹, X², . . . ), X′ (X^(1′), X^(2′), . . . ) andX″ (X^(1′)″, X²″, . . . ) are independently ligands with hydrolysablebonds to the associated metal or combinations thereof, M¹, M², . . . area non-tin metal ions, (0<(x1, x2, . . . )<3), (0<(z1, z2, . . . )<2),(1<(y1, y2, . . . )≤3), and n1, n2, . . . are determined by the valencyof M¹, M², . . . ions and the charge on X^(1″), X^(2″) . . . In general,M is a Group 2-Group 16 metal, and for many metals n ranges from 2 to 6.Desirable metals for M may include Hf, Zr, W, Ta, Co, Ni, In, Sb, Bi, Teor others. Representative suitable ML″_(n) compounds include, forexample, Zr(OtBu)₄, Hf(NMe)₄, In(O^(i)Pr)₃, and Sb(OEt)₃, which areavailable commercially from Sigma-Aldrich, Alfa Aesar, Gelest, StremChemical, and other suppliers. In some embodiments, all “a” parametervalues are zero such that all of the ligands are hydrolysed in situ. Infurther embodiments, 0.1≤(a1, a2, . . . )≤0.90, or 0.2<(a1, a2, . . .)≤0.85 or 0.25≤(a1, a2, . . . )≤0.75. In some embodiments, 0.25≤(b1, b2,. . . )≤1 or 0.3≤(b1, b2, . . . )≤0.95 or 0.35≤(b1, b2, . . . )≤0.9. Inadditional embodiments, 0≤(c1, c2, . . . )≤0.4 or 0.025≤(c1, c2, . . .)≤0.4 or 0.05≤(c1, c2, . . . )≤0.35 or 0.1≤(c1, c2, . . . )≤0.3, and0≤(d1, d2, . . . )≤0.5 or 0.025≤(d1, d2, . . . )≤0.4 or 0.05≤(d1, d2, .. . )≤0.3. A person of ordinary skill in the art will recognize thatadditional ranges of “a”, “b”, “c”, and “d” parameters within theexplicit ranges above are contemplated and are within the presentdisclosure. As used herein the symbols “<” and “≤” implicitly carry theconcept of the corresponding range limit being “about” the specifiedvalue within experimental error.

In summary, precursor compositions can comprise one or more compoundswith at least one having ligands with hydrolysable bonds to the metaland one or more having a hydrocarbyl ligand to provide radiationsensitivity. The compositions are generally engineered to be processableusing suitable organic solvents for the formation into precursorsolutions as described in the following section. The precursorsgenerally are engineered to provide desirable patterning properties aswell as good processability.

In some embodiments, the precursor compositions can comprise mixtures oftwo organotin compounds with different hydrocarbyl ligands, threeorganotin compounds with different hydrocarbyl ligands, or more thanthree organotin compounds with different hydrocarbyl ligands. Inaddition, precursor compositions can comprise a mixture of compoundswithout metal-carbon bonds and one or more compounds with radiationsensitive alkyl ligands having metal-carbon bonds. Generally, for binaryor tertiary mixtures, the mixture comprises at least about 5 molepercent of each component with distinct hydrocarbyl ligands, in someembodiments at least about 10 mole percent and in further embodiments atleast about 20 mole percent of each component with distinct hydrocarbylligands. A person of ordinary skill in the art will recognize thatadditional ranges of mole percent of components within the explicitranges above are contemplated and are within the present disclosure.

In some embodiments the precursor compositions comprise a mixture ofR—Sn moieties with hydrocarbyl ligands and inorganic metal SnX₄ orMX_(n) compounds without alkyl ligands bound directly to the metal.Generally, these mixtures comprises at least about 0.5 mole percent ofeach metal component, in some embodiments at least about 5 mole percentand in further embodiments at least about 10 mole percent of eachcomponent. A person of ordinary skill in the art will recognize thatadditional ranges of mixture components within the explicit ranges aboveare contemplated and are within the present disclosure. The componentsof the precursor compositions may be combined in solution and are notseparately formed as solid blends prior to, for example, formation of acoating.

Whether or not there are one or multiple distinct hydrocarbyl ligands,an R group can be a linear, branched, (i.e., secondary or tertiary atthe metal bonded carbon atom) or cyclic hydrocarbyl group. Each R groupindividually generally has from 1 to 31 carbon atoms with 3 to 31 carbonatoms for the secondary-bonded carbon atom and 4 to 31 carbon atoms forthe tertiary-bonded carbon atom embodiments, for example, methyl, ethyl,propyl, butyl, and branched alkyl. In particular, branched alkyl ligandsare desirable where the compound can be represented in anotherrepresentation by R¹R²R³CSnX₃, where R¹ and R² are independently analkyl group with 1-10 carbon atoms, and R³ is hydrogen or an alkyl groupwith 1-10 carbon atoms. In some embodiments R¹ and R² can form a cyclicalkyl moiety, and R₃ may also join the other groups in a cyclic moiety.Suitable branched alkyl ligands can be, for example, isopropyl (R¹ andR² are methyl and R³ is hydrogen), tert-butyl (R¹, R² and R³ aremethyl), tert-amyl (R¹ and R² are methyl and R³ is —CHCH₃), sec-butyl(R¹ is methyl, R² is —CHCH₃, and R³ is hydrogen), cyclohexyl,cyclopentyl, cyclobutyl, and cyclopropyl. Examples of suitable cyclicgroups include, for example, 1-adamantyl (—C(CH₂)₃(CH)₃(CH₂)₃ ortricyclo(3.3.1.13,7) decane bonded to the metal at a tertiary carbon)and 2-adamantyl (—CH(CH)₂(CH₂)₄(CH)₂(CH₂) or tricyclo(3.3.1.13,7) decanebonded to the metal at a secondary carbon). In other embodimentshydrocarbyl groups may include aryl, or alkenyl groups, for examplebenzyl, allyl, or alkynyl groups. In other embodiments the hydrocarbylligand R may include any group consisting solely of C and H, andcontaining 1-31 carbon atoms. For example: linear or branched alkyl(^(i)Pr, ^(t)Bu, Me, ^(n)Bu), cyclo-alkyl (cyclo-propyl, cyclo-butyl,cyclo-pentyl), olefinic (alkenyl, aryl, allylic), or alkynyl groups, orcombinations thereof. In further embodiments suitable R-groups mayinclude hydrocarble groups substituted with hetero-atom functionalgroups including cyano, thio, silyl, ether, keto, ester, or halogenatedgroups or combinations thereof.

Some suitable metal compositions with desired ligand structures can bepurchased from commercial sources, such as Alfa Aesar (MA, USA) and TCIAmerica (OR, USA), and other metal-ligand compositions can besynthesized as described below. Low metal contaminant precursorcompositions can be synthesized using the methods described herein basedon the use of suitably low contaminated starting materials andappropriate purification.

Desirable patterning results have been obtained using a precursorcompound with branched alkyl ligands. But fuller advantage of ligandselection has been achieved through the use of mixed alkyl ligands, asseparately advantageous patterning properties such as dose andline-width-roughness imparted by different ligands may be obtainedthrough the teachings herein through blending of multiple alkyl ligandsas illustrated in the examples provided. The processing with in situhydrolysed precursors provides for effective use of tin compounds withmethyl ligands in the precursor solutions based on desirable solvents.Effective patterning with a mixture of tert-butyl ligands and methylligands is described in the Examples below as well as a precursorcomprising a mixture of a hydrolysable compound with t-butyl ligands andhydrolysable SnX₄ compounds (X=NMe²⁻ or X=O^(t)Bu).

It has been found that the radiation curing doses can scaleapproximately linearly for mixtures of precursor compounds withdifferent alkyl ligands based on the radiation doses for the respectiveindividual precursor compounds. Due to the lower radiation doses thatcan be used with the branched alkyl ligands, it is generally desirablefor the mixtures to comprise at least one branched organic ligand. Butcorrespondingly it has been discovered that the line width roughness canbe improved with mixtures of precursor compounds with different organicligands. While not wanting to be limited by theory, it is possible thatthe improved line width roughness values observed for the mixturecompositions may be due to facilitated etchings for the mixturecompositions without significantly diminishing the contrast in thepattern. In this context, the observations may extend to mixturecompositions containing combinations of organotin compounds bearingbranched or unbranched alkyls.

X, X′, and X″ ligands are generally Lewis bases that can react suitablywith acidic protons of water or other Lewis acids via hydrolysis orsolvolysis of M-X, M-X′ and M-X″ bonds to form readily volatilizedproducts. Alternatively these ligands may react with an appropriatereagent via oxidation or reduction reactions to form readily volatilizedproducts. Ligands may generally be classified by the acid dissociationconstant (pK_(a)) of their conjugate acids, where desirable ligands forsome embodiments have conjugate acid pKas greater than about 4. Thus, X,X′ and X″ generally comprise an atom binding to the metal, e.g., tin,that can undergo nucleophilic substitution involving H₂O and —OH. Theresulting M-OH or M-OH₂ ligands may then react via subsequentcondensation or dehydration steps to form an oxide-hydroxide network.

Suitable ligands comprise alkylamido or dialkylamido (—NR¹R², where R¹and R² are independently hydrocarbon groups with 1-10 carbon atoms orhydrogen), siloxo (—OSiR¹R²R³, where R¹, R^(2′) are independentlyhydrocarbon groups with 1-10 carbon atoms), silylamido (—N(SiR¹ ₃)(R²),where R¹ and R² are independently hydrocarbon groups with 1-10 carbonatoms), disilylamido (—N(SiR¹ ₃)(SiR² ₃) where R¹ and R² areindependently hydrocarbon groups with 1-10 carbon atoms), alkoxo andaryloxo (—OR, where R is an alkyl or aryl group with 1-10 carbon atoms),azido (—N₃), alkynido (—C≡CR, where R is a hydrocarbon group with 1-9carbon atoms), amidato (—NR¹(COR²) where R¹ and R² are independentlyhydrocarbon groups with 1-7 carbon atoms or hydrogen), amidinato(—NR¹C(NR²)R³) where R¹ and R² are independently hydrocarbon groups with1-8 carbon atoms or hydrogen), imido (—N(COR¹)(COR²), where R¹ and R²are independently hydrocarbon groups with 1-8 carbon atoms or hydrogen),or fluorinated analogues thereof.

The metal in an inorganic or organometallic material can significantlyinfluence the absorption of radiation. Tin provides strong absorption ofextreme ultraviolet light at 13.5 nm. In combination with alkyl ligands,metals also provide strong absorption of ultraviolet light at 193 nmwavelength. Tin also provides good absorption of electron-beamradiation. The energy absorbed is modulated by the metal-organicinteractions, which can result in the rupturing of the metal-ligand bondand the desired control over the material properties. Nevertheless,other metal compositions can be introduced to further influence theabsorption properties and overall resist performance. As noted above,other non-tin metals are generally introduced as MX_(n), where X is aligand having a hydrolysable bond to the metal.

The use of precursor compounds with ligands having hydrolysable bonds tothe metal can simplify the preparation of the precursor solutions sincein situ hydrolysis avoids the many synthetic and isolation stepsrequired to produce a defined hydrolysis product. In particular, thesolution phase hydrolysis and subsequent condensation and isolation ofan organotin oxide hydroxide hydrolysate can involve significantsolubility changes during the reaction, so that avoiding this solutionbased step avoids a potentially difficult process step. To the extentthat an ingredient of the precursor composition comprises a separatelyhydrolysed component, this particular component can be obtained using asolution based hydrolysis, such as using a base catalyzed aqueoussolution, as described in the '839 application. The components withligands having hydrolysable bonds to the metal can generally bepurchased or synthesized from appropriate starting materials, forexample from a tin halide composition or tetrakis(dialkylamido)tincomposition, as noted in the Examples.

Precursor Solution Formations and Coating Properties

A range of precursor solutions can be formulated based on thecompositions described in the previous section. The precursorcompositions generally have the commonality of involving some degree ofhydrolytically sensitive metal-ligand bonds. For precursor compoundshaving sufficient vapor pressure, the hydrolysis can be alternativelyperformed in situ in a coating or as part of a vapor phase depositionprocess. The precursor solutions for solution deposition generallycomprise tin cations and optionally one or more non-tin metal cations inan organic solvent.

The concentration of ligand stabilized metal cations in the solution canbe selected to provide suitable solution properties for a particularsolution deposition approach, such as spin coating, slot coating, dipcoating, spray or aerosol coating, or printing, and are designed to forma coating composition upon at least partial solvent removal andultimately an inorganic solid dominated by tin oxides upon irradiationand/or thermal treatment, exposure to a plasma, or similar processing.

With the precursor solutions based on alkyl-stabilization ligands and anorganic solvent, progression to the oxide can be controlled as part ofthe procedure for processing the solution first to a coating materialand then to the ultimate metal oxide composition with organic ligandsthrough hydrolysis and condensation reactions with ambient water vaporduring coating and/or hydrolysis and condensation following coating. Asdescribed herein, alkyl ligands, especially branched alkyl ligandsand/or combinations of alkyl ligands in particular stoichiometriesrelative to the metal, can be used to provide significant control to theprocessing of the solution to an effective radiation resist composition.Processing with an alcohol based solvent can involve partial or completesubstitution of alkoxy ligands from the alcohol for initial ligands withhydrolysable bonds to the metal, but such substitution may not alterdownstream processing in any significant way.

A precursor solution concentration can be conveniently specified basedon tin ion molar concentration and concentrations of any other metalscan be correspondingly specified through the molar fraction values forthe metals relative to tin. In general, the precursor solution comprisesfrom about 0.005 M to about 1.4 M tin cation, in further embodimentsfrom about 0.02 M to about 1.2 M, and in additional embodiments fromabout 0.1 M to about 1.0 M tin cation. Total non-tin metal in theprecursor solution generally can range from about 0.025 mole % to about10 mole % of the total metal ions and in further embodiments from about10 mole % to about 50 mole % of the total metal ions. A person ofordinary skill in the art will recognize that additional ranges of tincations within the explicit ranges above are contemplated and are withinthe present disclosure.

In general, the desired hydrolysate compounds can be dissolved in anorganic solvent, e.g., alcohols, aromatic and aliphatic hydrocarbons,esters or combinations thereof. In particular, suitable solventsinclude, for example, aromatic compounds (e.g., xylenes, toluene),ethers (anisole, tetrahydrofuran), esters (propylene glycol monomethylether acetate, ethyl acetate, ethyl lactate), alcohols (e.g.,4-methyl-2-propanol, 1-butanol, methanol, isopropyl alcohol,1-propanol), ketones (e.g., methyl ethyl ketone), mixtures thereof, andthe like. In general, organic solvent selection can be influenced bysolubility parameters, volatility, flammability, toxicity, viscosity andpotential chemical interactions with other processing materials. Afterthe components of the solution are dissolved and combined, the characterof the species may change as a result of partial in-situ hydrolysis,hydration, and/or condensation. When the composition of the solution isreferenced herein, the reference is to the components as added to thesolution, since complex formulations may undergo solvolysis and ligandmetathesis, or produce metal polynuclear species in solution that maynot be well characterized. For certain applications it is desirable forthe organic solvent to have a flash point of no less than about 10° C.,in further embodiments no less than about 20° C. and in furtherembodiment no less than about 25° C. and a vapor pressure at 20° C. ofno more than about 10 kPa, in some embodiments no more than about 8 kPaand in further embodiments no more than about 6 kPa. A person ofordinary skill in the art will recognize that additional ranges of flashpoint and vapor pressure within the explicit ranges above arecontemplated and are within the present disclosure.

The concentrations of the species in the precursor solutions can beselected to achieve desired physical properties of the solution. Inparticular, lower concentrations overall can result in desirableproperties of the solution for certain coating approaches, such as spincoating, that can achieve thinner coatings using reasonable coatingparameters. It can be desirable to use thinner coatings to achieveultrafine patterning as well as to reduce material costs. In general,the concentration can be selected to be appropriate for the selectedcoating approach. Coating properties are described further below.

In general, precursor solutions can be well mixed using appropriatemixing apparatuses suitable for the volume of material being formed.Suitable filtration can be used to remove any contaminants or othercomponents that do not appropriately dissolve. In some embodiments, itmay be desirable to form separate solutions that can be combined to formthe precursor solution from the combination. Specifically, separatesolutions can be formed comprising one or more of the compoundsindicated above in Formula (1). Generally, the separate solutions or thecombined solutions can be well mixed. The resulting solution can bereferred to as a stabilized metal cation solution.

Stability of the precursor solutions can be evaluated with respect tochanges relative to the initial solution. Specifically, a solution haslost stability if phase separation occurs with the production of largesol particles or if the solution loses its ability to perform desiredpattern formation. Based on the improved stabilization approachesdescribed herein, the solutions can be stable for at least about a weekwithout additional mixing, in further embodiments at least about 2weeks, in other embodiments at least about 4 weeks. A person of ordinaryskill in the art will recognize that additional ranges of stabilizationtimes are contemplated and are within the present disclosure. Suitablesolutions generally can be formulated with sufficient stabilizationtimes that the solutions can be commercially distributed withappropriate shelf lives.

As described herein, processing approaches have been developed thatprovide for reduction of metal contamination. Thus, the precursorsolutions can be formulated that have very low levels of non-tin metal.In general, the unintentional metal concentrations can all beindividually reduced to values of no more than about 1 part per millionby weight (ppm) in further embodiments, no more than about 200 parts perbillion by weight (ppb), in additional embodiments no more than about 50ppb, and in other embodiments no more than about 10 ppb. In someembodiments, it may be desirable to add other metal elements toinfluence processing, and generally these can be identified by levels ofat least about 1 weight percent and in some embodiments at least about 2weight percent, and can thus be distinguished from contaminant metals,if appropriate. Metal contaminants to be decreased in particular includealkali metals and alkaline earth metals, Au, Ag, Cu, Fe, Pd, Pt, Co, Mn,and Ni. A person or ordinary skill in the art will recognize thatadditional ranges of metal levels within the explicit levels above arecontemplated and are within the present disclosure.

Previous efforts to produce precursor solutions and coatings with lowmetal contamination are described in the '839 application. Using vaporwater for hydrolysis provides a hydrolysis reactant substantially freeof metal contaminants that can effectively further the formation of alow contaminant patternable coating based on a low contaminant tincomposition. Suitable starting materials with low metal contaminationcan be obtained commercially or through purification.

Coating Processing and Hydrolysis In Situ

A coating material can be formed through deposition and subsequentprocessing of the precursor solution onto a selected substrate. Usingthe precursor solutions described herein, some hydrolysis andcondensation generally is performed during coating, and may be completedor furthered post coating via subsequent processing steps such asheating in air. A substrate generally presents a surface onto which thecoating material can be deposited, and the substrate may comprise aplurality of layers in which the surface relates to an upper most layer.In some embodiments, the substrate surface can be treated to prepare thesurface for adhesion of the coating material. Also, the surface can becleaned and/or smoothed as appropriate. Suitable substrate surfaces cancomprise any reasonable material. Some substrates of particular interestinclude, for example, silicon wafers, silica substrates, other inorganicmaterials such as ceramic materials, polymer substrates, such as organicpolymers, composites thereof and combinations thereof across a surfaceand/or in layers of the substrate. Wafers, such as relatively thincylindrical structures, can be convenient, although any reasonableshaped structure can be used. Polymer substrates or substrates withpolymer layers on non-polymer structures can be desirable for certainapplications based on their low cost and flexibility, and suitablepolymers can be selected based on the relatively low processingtemperatures that can be used for the processing of the patternablematerials described herein. Suitable polymers can include, for example,polycarbonates, polyimides, polyesters, polyalkenes, copolymers thereofand mixtures thereof. In general, it is desirable for the substrate tohave a flat surface, especially for high resolution applications.However, in specific embodiments the substrate may possess substantialtopography, where the resist coating is intended to fill or planarizefeatures for particular patterning applications. Alternatively, usingthe vapor deposition methods described herein, existing topography andfeatures may be conformally coated with organotin oxide hydroxide photoresist for particular patterning applications.

In general, any suitable solution coating process can be used to deliverthe precursor solution to a substrate in addition to the vapordeposition processes disclosed herein. Suitable coating approaches caninclude, for example, spin coating, spray coating, dip coating, knifeedge coating, printing approaches, such as inkjet printing and screenprinting, and the like. Some of these coating approaches form patternsof coating material during the coating process, although the resolutionavailable currently from printing or the like has a significantly lowerlevel of resolution than available from radiation based patterning asdescribed herein.

If patterning is performed using radiation, spin coating can be adesirable approach to cover the substrate relatively uniformly, althoughthere can be edge effects. In some embodiments, a wafer can be spun atrates from about 500 rpm to about 10,000 rpm, in further embodimentsfrom about 1000 rpm to about 7500 rpm and in additional embodiments fromabout 2000 rpm to about 6000 rpm. The spinning speed can be adjusted toobtain a desired coating thickness. The spin coating can be performedfor times from about 5 seconds to about 5 minutes and in furtherembodiments from about 15 seconds to about 2 minutes. An initial lowspeed spin, e.g. at 50 rpm to 250 rpm, can be used to perform an initialbulk spreading of the composition across the substrate. A back siderinse, edge bead removal step or the like can be performed with water orother suitable solvent to remove any edge bead. A person or ordinaryskill in the art will recognize that additional ranges of spin coatingparameters within the explicit ranges above are contemplated and arewithin the present disclosure.

The thickness of the coating generally can be a function of theprecursor solution concentration, viscosity and the spin speed for spincoating. For other coating processes, the thickness can generally alsobe adjusted through the selection of the coating parameters. In someembodiments, it can be desirable to use a thin coating to facilitateformation of small and highly resolved features in the subsequentpatterning process. For example, the coating materials after drying canhave an average thickness of no more than about 10 microns, in otherembodiments no more than about 1 micron, in further embodiments no morethan about 250 nanometers (nm), in additional embodiments from about 1nanometers (nm) to about 50 nm, in other embodiments from about 2 nm toabout 40 nm and in some embodiments from about 3 nm to about 25 nm. Aperson of ordinary skill in the art will recognize that additionalranges of thicknesses within the explicit ranges above are contemplatedand are within the present disclosure. The thickness can be evaluatedusing non-contact methods of x-ray reflectivity and/or ellipsometrybased on the optical properties of the film. In general, the coatingsare relatively uniform to facilitate processing. In some embodiments,the variation in thickness of the coating varies by no more than ±50%from the average coating thickness, in further embodiments no more than±40% and in additional embodiments no more than about ±25% relative tothe average coating thickness. In some embodiments, such as highuniformity coatings on larger substrates, the evaluation of coatinguniformity may be evaluated with a 1 centimeter edge exclusion, i.e.,the coating uniformity is not evaluated for portions of the coatingwithin 1 centimeter of the edge. A person of ordinary skill in the artwill recognize that additional ranges within the explicit ranges aboveare contemplated and are within the present disclosure.

The coating process itself can result in the evaporation of a portion ofthe solvent since many coating processes form droplets or other forms ofthe coating material with larger surface areas and/or movement of thesolution that stimulates evaporation. The loss of solvent tends toincrease the viscosity of the coating material as the concentration ofthe species in the material increases. An objective during the coatingprocess can be to remove sufficient solvent to stabilize the coatingmaterial for further processing. Reactive species may condense duringcoating or subsequent heating to forming a hydrolysate coating material.

In general, the coating material can be exposed to, and optionallyheated in, the presence of atmospheric moisture prior to radiationexposure to hydrolyse the hydrolysable bonds to the metal in theprecursor compositions, and/or further drive off solvent and promotedensification of the coating material. The coating material following insitu hydrolysis may generally form a polymeric metal oxo-hydroxo networkbased on the binding oxo-hydroxo ligands to the metals in which themetals also have some alkyl ligands, or a molecular solid comprised ofpolynuclear metal oxo/hydroxo species with alkyl ligands.

The hydrolysis/solvent removal process may or may not be quantitativelycontrolled with respect to precise stoichiometry of the heated coatingmaterial and/or specific amounts of solvent remaining in the coatingmaterial. Additionally, the formulas and compositions expressed hereinmay contain some additional water, whether directly bound to Sn, or ashydrogen-bonded component of the network. Empirical evaluation of theresulting coating material properties generally can be performed toselect processing conditions that are effective for the patterningprocess. While heating may not be needed for successful application ofthe process, it can be desirable to heat the coated substrate to speedthe processing and/or to increase the reproducibility of the processand/or to facilitate vaporization of the hydrolysis by products, such asamines and/or alcohols. In embodiments in which heat is applied toremove solvent, the coating material can be heated to temperatures fromabout 45° C. to about 250° C. and in further embodiments from about 55°C. to about 225° C. The heating for solvent removal can generally beperformed for at least about 0.1 minute, in further embodiments fromabout 0.5 minutes to about 30 minutes and in additional embodiments fromabout 0.75 minutes to about 10 minutes. A person of ordinary skill inthe art will recognize that additional ranges of heating temperature andtimes within the explicit ranges above are contemplated and are withinthe present disclosure. As a result of the heat treatment, hydrolysis,and densification of the coating material, the coating material canexhibit an increase in index of refraction and in absorption ofradiation without significant loss of contrast.

Vapor Based Coating Formation

The development of precursor compounds comprising of both R-groups withsubstantially non-hydrolysable bonds to Sn, and X ligands withhydrolysable bonds to Sn has been exploited for the development of vaporphase deposition of radiation patternable organotin oxide hydroxidecoatings. In particular, the relatively high vapor pressures andreactivity of many R_(n)SnX_((4-n)) compounds such as those listed inTable 1, make possible the use of vapor deposition methods fordeposition of organotin oxide hydroxide thin-film photoresists. Throughthe introduction the hydrolysable precursors in the vapor phase in areactor closed from the ambient atmosphere, the hydrolysis can beperformed as part of the deposition process, i.e., a chemical vapordeposition. Potential vapor deposition methods include chemical vapordeposition (CVD), atomic layer deposition (ALD), and modificationsthereof, many of which have previously been employed to depositinorganic metal oxide and nitride films with metal alkylamide, alkoxide,and halide precursors, [1-4] including SnO₂ from Sn(NMe₂)₄. [5]. Toperform the vapor deposition, generally one or more metal-containingprecursors are reacted on or more with small molecule gas-phase reagentssuch as H₂O, H₂O₂, O₃, O₂, or CH₃OH, which serve as O and H sources forproduction of oxides and oxide hydroxides. If desired, physical vapordeposition approaches can also be performed in which the precursorcompositions with ligands having hydrolysable bonds to Sn are depositedfrom the vapor phase and the bonds subsequently hydrolysed after coatingformation, but for vapor phase processing, hydrolysis/oxidation duringthe deposition generally may be more efficient.

TABLE 1 Compound Vapor Pressure (torr) Temperature (° C.)^(t)BuSn(NEt₂)₃ 0.3 95 ^(t)BuSn(NMe₂)₃ 0.3 55 ^(t)BuSn(O^(t)Bu)3 3.5 ~82^(i)PrSn(NMe₂)₃ 1.4 53 Sn(NEt₂)₄ 0.5 110 Sn(NMe₂)₄ 0.1 ~54 Sn(O^(t)Bu)₄0.3 65 Sn(O^(t)Am)4 2 120 MeSn(O^(t)Bu)₃ 0.1 ~57 ^(n)BuSn(O^(t)Bu)₃ 0.9100 ^(n)BuSn(NMe₂)₃ 0.05 80

In CVD methods, two or more reactant gases are generally mixed in thechamber in the vicinity of the substrate surface. Therefore, sufficientstability can be designed into the reaction conditions to controlundesirable vapor-phase reactions and nucleation. ALD precursors,introduced separately and sequentially to the reaction chamber,typically react with chemisorbed co-precursor or decomposition productssaturating the substrate surface. Desirable features of R_(n)SnX_((4-n))precursors include, for example, sufficient volatility for vapor-phasetransport in the system, thermal stability to prevent prematuredecomposition, and appropriate reactivity with co-precursors to producethe target product under prescribed process conditions. The pressure andtemperature in the reaction chamber can be selected to control thereaction process.

In general, precursors with relatively low vapor pressures may beintroduced using flow of vapor, aerosol, and/or direct liquid injectioninto a vaporization chamber. Flash evaporators can be used to introducea controlled amount of precursor vapors into the reaction chamber tocorrespondingly control the reaction process in the chamber. Thesecondary reactant to drive hydrolysis/oxidation can be introducedthrough a separate inlet into the chamber. Commercial CVD apparatusescan be adapted for this use or specific equipment can be used. Tofacilitate deposition the substrate may be heated or may be cooleddepending on the precursor properties. Inert gases such as N₂, Ar or thelike may be used in appropriate capacities as carrier gases, purgegases, or pressure modulating gases in both sequential and continuousflow regimes.

FIG. 16 illustrates apparatus 150 for the formation of an organotinoxide hydroxide layer on a substrate. Deposition chamber 151 interfaceswith inlet 152, separate inlet 154 and outlet 153 connected with pump155 and pump 156. Substrate 157 is mounted within the interior ofdeposition chamber 151 on thermal block 158. In this embodiment, vessel168 is depicted as a bubbler connected to supply of inert gas 170.Structure 160 is configured to supply organotin compound 164 todeposition chamber 151 through inlet 152. Apparatus 150 also depictsstructure 174, configured to deliver a second precursor vapor todeposition chamber 151 through separate inlet 154. Apparatus 150 alsodepicts structure 180, configured to supply third precursor vapor 178 todeposition chamber 151 through inlet 176.

A range of R_(n)SnX_((4-n)) compounds where n=0, 1, or 2, orcombinations thereof, as demonstrated to produce organotin oxidehydroxide photoresists by hydrolysis in solution or in-situ hydrolysisas discussed herein, may also be suitable for vapor deposition oforganotin oxide hydroxide photoresists with desirable properties. UsefulX ligands include alkylamido and dialkylamido, chloro, alkoxo, oralkynido, siloxo, silylamido, disilylamido, aryloxo, azido, amidato,amidinato, or fluorinated analogues thereof in combination withhydrocarbyl R groups that include both straight-chain and branched-chainalkyl, cyclo-alkyl, aryl, alkenyl, alkynyl benzyl, and their fluorinatedderivatives. Suitable precursors may include, for example,(CH₃)₃CSn(NMe₂)₃, (CH₃)₂CHSn(NMe₂)₃, (CH₃)₂(CH₃CH₂)CSn(NMe₂)₃,(CH₂)₂CHSn(NMe₂)₃, CH₃Sn(NMe₂)₃, (CH₂)₃CHSn(NMe₂)₃, (CH₂)₄CHSn(NMe₂)₃,(C₆H₅)CH₂Sn(NMe₂)₃, (C₆H₅)(CH₃)CHSn(NMe₂)₃, (C₆H₅)(CH₃)CHSn(NMe₂)₃,(CH₃)₂(CN)CSn(NMe₂)₃, (CH₃)(CN)CHSn(NMe₂)₃, or (CH₃)₃CSn(O^(t)Bu)₃,(CH₃)₂CHSn(O^(t)Bu)₃, (CH₃)₂(CH₃CH₂)CSn(O^(t)Bu)₃, (CH₂)₂CHSn(O^(t)Bu)₃,CH₃Sn(O^(t)Bu)₃, (CH₂)₃CHSn(O^(t)Bu)₃, (CH₂)₄CHSn(O^(t)Bu)₃,(C₆H₅)CH₂Sn(O^(t)Bu)₃, (C₆H₅)(CH₃)CHSn(O^(t)Bu)₃,(C₆H₅)(CH₃)CHSn(O^(t)Bu)₃, (CH₃)₂(CN)CSn(O^(t)Bu)₃,(CH₃)(CN)CHSn(O^(t)Bu)₃ or others known to those skilled in the art.Additionally, one or more vapor-phase precursor compounds with=0 such asSn(NMe₂)₄, or Sn(OtBu)₄ may be reacted sequentially or concurrently withthe organotin-containing precursors to alter the R:Sn ratio in the filmto achieve desirable patterning attributes.

Thus hydrolysable compounds can be directly deposited via vapor phasehydrolysis as the corresponding alkyl tin oxide hydroxide coating, whichcan then be appropriately patterned. Advantages of vapor deposition mayinclude, for example, reduced resist film defect density, improvedthickness and compositional uniformity, as well as conformal andside-wall coating of substrate topography.

A vapor deposition method for direct deposition of organotin oxidehydroxides with the general formulae RSnO_((3/2-x/2))(OH)_(x) (0<x<3)and can comprise in some embodiments an inert gas source connected toseparate heated bubbler vessels. A first vessel contains a liquid alkyltris(dialkylamido)tin compound of sufficient vapor pressure to producesuitable partial pressures for transport in the inert carrier gas. Asecond vessel contains liquid water or a water/alcohol mix. Bycontrolling vessel temperatures, inert gas flow rate, and total systempressure, vapor-phase RSn(NR′₂)₃ and H₂O are transported independentlyto a chamber evacuated to <˜0.1 Torr, more generally from about 0.01Torr to about 25 Torr, and in some atmospheric pressure CVDpressures >25 Torr. The precursors therein mix and react to deposit anorganotin oxide hydroxide on the substrate. The substrate and/or chamberand/or vapors may be heated to promote reaction and deposition on thesubstrate surface. Reaction temperatures below about 200° C. can bedesirable in some embodiments to limit de-alkylation of the tin compoundand/or to prevent excessive dehydration and condensation of the oxidehydroxide. Such oxide hydroxide formation may reduce photoresistdissolution-rate contrast between exposed and unexposed regions. Thegases, the chamber walls and/or the substrate can be heated in variousembodiments, generally to a temperature from about 40° C. to about 175°C. and in further embodiments from about 50° C. to about 160° C. Aperson of ordinary skill in the art will recognize that additionalranges of pressure and temperature within the explicit ranges above arecontemplated and re within the present disclosure. In a similar, relatedprocess, pulses of water vapor, inert gas, and RSn(NR′₂)₃ of appropriateduration and frequency may be alternated to enable a surface-limitedadsorption and reaction regime common to ALD methodologies.

Patterning and Patterned Structure Properties

Following hydrolysis, condensation, and drying, the coating material canbe finely patterned using radiation. As noted above, the composition ofthe precursor solution and thereby the corresponding coating materialcan be designed for sufficient absorption of a desired form ofradiation. The absorption of the radiation results in energy that canbreak the bonds between the metal and alkyl ligands so that at leastsome of the alkyl ligands are no longer available to stabilize thematerial. Radiolysis products, including alkyl ligands or fragments maydiffuse out of the film, or not, depending on process variables and theidentity of such products. With the absorption of a sufficient amount ofradiation, the exposed coating material condenses, i.e. forms anenhanced metal oxo-hydroxo network, which may involve additional waterabsorbed from the ambient atmosphere. The radiation generally can bedelivered according to a selected pattern. The radiation pattern istransferred to a corresponding pattern or latent image in the coatingmaterial with irradiated areas and un-irradiated areas. The irradiatedareas comprise chemically altered coating material, and theun-irradiated areas comprise generally the as-formed coating material.As noted below, very smooth edges can be formed upon development of thecoating material with the removal of the un-irradiated coating materialor alternatively with selective removal of the irradiated coatingmaterial.

Radiation generally can be directed to the coated substrate through amask or a radiation beam can be controllably scanned across thesubstrate. In general, the radiation can comprise electromagneticradiation, an electron-beam (beta radiation), or other suitableradiation. In general, electromagnetic radiation can have a desiredwavelength or range of wavelengths, such as visible radiation,ultraviolet radiation or x-ray radiation. The resolution achievable forthe radiation pattern is generally dependent on the radiationwavelength, and a higher resolution pattern generally can be achievedwith shorter wavelength radiation. Thus, it can be desirable to useultraviolet light, x-ray radiation or an electron-beam to achieveparticularly high resolution patterns.

Following International Standard ISO 21348 (2007) incorporated herein byreference, ultraviolet light extends between wavelengths of greater thanor equal 100 nm and less than 400 nm. A krypton fluoride laser can beused as a source for 248 nm ultraviolet light. The ultraviolet range canbe subdivided in several ways under accepted Standards, such as extremeultraviolet (EUV) from greater than or equal 10 nm to less than 121 nmand far ultraviolet (FUV) from greater than or equal to 122 nm to lessthan 200 nm A 193 nm line from an argon fluoride laser can be used as aradiation source in the FUV. EUV light has been used for lithography at13.5 nm, and this light is generated from a Xe or Sn plasma sourceexcited using high energy lasers or discharge pulses. Soft x-rays can bedefined from greater than or equal 0.1 nm to less than 10 nm.

The amount of electromagnetic radiation can be characterized by afluence or dose which is defined by the integrated radiative flux overthe exposure time. Suitable radiation fluences can be from about 1mJ/cm² to about 150 mJ/cm², in further embodiments from about 2 mJ/cm²to about 100 mJ/cm², and in further embodiments from about 3 mJ/cm² toabout 50 mJ/cm². A person of ordinary skill in the art will recognizethat additional ranges of radiation fluences within the explicit rangesabove are contemplated and are within the present disclosure.

With electron-beam lithography, the electron beam generally inducessecondary electrons which generally modify the irradiated material. Theresolution can be a function at least in part of the range of thesecondary electrons in the material in which a higher resolution isgenerally believed to result from a shorter range of the secondaryelectrons. Based on high resolution achievable with electron-beamlithography using the inorganic coating materials described herein, therange of the secondary electrons in the inorganic material is limited.Electron beams can be characterized by the energy of the beam, andsuitable energies can range from about 5 V to about 200 kV (kilovolt)and in further embodiments from about 7.5 V to about 100 kV.Proximity-corrected beam doses at 30 kV can range from about 0.1microcoulombs per centimeter squared to about 5 millicoulombs percentimeter squared (mC/cm²), in further embodiments from about 0.5μC/cm² to about 1 mC/cm² and in other embodiments from about 1 μC/cm² toabout 100 μC/cm². A person of ordinary skill in the art can computecorresponding doses at other beam energies based on the teachings hereinand will recognize that additional ranges of electron beam propertieswithin the explicit ranges above are contemplated and are within thepresent disclosure.

Based on the design of the coating material, there can be a largecontrast of material properties between the irradiated regions that havecondensed coating material and the un-irradiated, coating material withsubstantially intact organic ligands. It has been found that thecontrast at a given dose can be improved with a post-irradiation heattreatment, although satisfactory results can be achieved in someembodiments without post-irradiation heat treatment. The post-exposureheat treatment seems to anneal the irradiated coating material toincrease its condensation without significantly condensing theun-irradiated regions of coating material based on thermal breaking ofthe organic ligand-metal bonds. For embodiments in which a postirradiation heat treatment is used, the post-irradiation heat treatmentcan be performed at temperatures from about 45° C. to about 250° C., inadditional embodiments from about 50° C. to about 190° C. and in furtherembodiments from about 60° C. to about 175° C. The post exposure heatingcan generally be performed for at least about 0.1 minute, in furtherembodiments from about 0.5 minutes to about 30 minutes and in additionalembodiments from about 0.75 minutes to about 10 minutes. A person ofordinary skill in the art will recognize that additional ranges ofpost-irradiation heating temperature and times within the explicitranges above are contemplated and are within the present disclosure.This high contrast in material properties further facilitates theformation of high-resolution lines with smooth edges in the patternfollowing development as described in the following section.

Following exposure with radiation, the coating material is patternedwith irradiated regions and un-irradiated regions. Referring to FIGS. 1and 2, a patterned structure 100 is shown comprising a substrate 102, athin film 103 and patterned coating material 104. Patterned coatingmaterial 104 comprises regions 110, 112, 114, 116 of irradiated coatingmaterial and uncondensed regions 118, 120, 122 of un-irradiated coatingmaterial. The pattern formed by condensed regions 110, 112, 114, 116 anduncondensed regions 118, 120, 122 represent a latent image into thecoating material, and the development of the latent image is discussedin the following section.

Development and Patterned Structure

Development of the image involves the contact of the patterned coatingmaterial including the latent image to a developer composition to removeeither the un-irradiated coating material to form the negative image orthe irradiated coating to form the positive image. Using the resistmaterials described herein, effective negative patterning or positivepatterning generally can be performed with desirable resolution usingappropriate developing solutions, and generally based on the samecoating. In particular, the irradiated regions are at least partiallycondensed to increase the metal oxide character so that the irradiatedmaterial is resistant to dissolving by organic solvents while theun-irradiated compositions remain soluble in the organic solvents.Reference to a condensed coating material refers to at least partialcondensation in the sense of increasing the oxide character of thematerial relative to an initial material. On the other hand, theun-irradiated material is less soluble in weak aqueous bases or acidsdue to the hydrophobic nature of the material so that aqueous bases canbe used to remove the irradiated material while maintaining thenon-irradiated material for positive patterning.

The coating compositions with organic-stabilization ligands produce amaterial that is inherently hydrophobic. Irradiation to break at leastsome of the organic metal bonds converts the material into a lesshydrophobic, i.e., more hydrophilic, material. This change in characterprovides for a significant contrast between the irradiated coating andnon-irradiated coating that provides for the ability to do both positivetone patterning and negative tone patterning with the same resistcomposition. Specifically, the irradiated coating material condenses tosome degree into a more of a metal oxide composition; however, thedegree of condensation generally is moderate without significant heatingso that the irradiated material is relatively straightforward to developwith convenient developing agents.

With respect to negative tone imaging, referring to FIGS. 3 and 4, thelatent image of the structure shown in FIGS. 1 and 2 has been developedthrough contact with a developer to form patterned structure 130. Afterdevelopment of the image, substrate 102 is exposed along the top surfacethrough openings 132, 134, 135. Openings 132, 134, 135 are located atthe positions of uncondensed regions 118, 120, 122 respectively. Withrespect to positive tone imaging, referring to FIGS. 5 and 6, the latentimage of the structure shown in FIGS. 1 and 2 has been developed to formpatterned structure 140. Patterned structure 140 has the conjugate imageof patterned structure 130. Patterned structure 140 has substrate 102exposed at positions of irradiated regions 110, 112, 114, 116 that aredeveloped to form openings 142, 144, 146, 148.

For the negative tone imaging, the developer can be an organic solvent,such as the solvents used to form the precursor solutions. In general,developer selection can be influenced by solubility parameters withrespect to the coating material, both irradiated and non-irradiated, aswell as developer volatility, flammability, toxicity, viscosity andpotential chemical interactions with other process material. Inparticular, suitable developers include, for example, aromatic compounds(e.g., benzene, xylenes, toluene), esters (e.g., propylene glycolmonomethyl ester acetate, ethyl acetate, ethyl lactate, n-butyl acetate,butyrolactone), alcohols (e.g., 4-methyl-2-pentanol, 1-butanol,isopropanol, 1-propanol, methanol), ketones (e.g., methyl ethyl ketone,acetone, cyclohexanone, 2-heptanone, 2-octanone), ethers (e.g.,tetrahydrofuran, dioxane, anisole) and the like. The development can beperformed for about 5 seconds to about 30 minutes, in furtherembodiments from about 8 seconds to about 15 minutes and in additionembodiments from about 10 seconds to about 10 minutes. A person ofordinary skill in the art will recognize that additional ranges withinthe explicit ranges above are contemplated and are within the presentdisclosure.

For positive tone imaging, the developer generally can be aqueous acidsor bases. In some embodiments, aqueous bases can be used to obtainsharper images. To reduce contamination from the developer, it can bedesirable to use a developer that does not have metal atoms. Thus,quaternary ammonium hydroxide compositions, such as tetraethylammoniumhydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxideor combinations thereof, are desirable as developers. In general, thequaternary ammonium hydroxides of particular interest can be representedwith the formula R₄NOH, where R=a methyl group, an ethyl group, a propylgroup, a butyl group, or combinations thereof. The coating materialsdescribed herein generally can be developed with the same developercommonly used presently for polymer resists, specifically tetramethylammonium hydroxide (TMAH). Commercial TMAH is available at 2.38 weightpercent, and this concentration can be used for the processing describedherein. Furthermore, mixed quaternary tetraalkyl-ammonium hydroxides canbe used. In general, the developer can comprise from about 0.5 to about30 weight percent, in further embodiments from about 1 to about 25weight percent and in other embodiments from about 1.25 to about 20weight percent tetra-alkylammonium hydroxide or similar quaternaryammonium hydroxides. A person of ordinary skill in the art willrecognize that additional ranges of developer concentrations within theexplicit ranges above are contemplated and are within the presentdisclosure.

In addition to the primary developer composition, the developer cancomprise additional compositions to facilitate the development process.Suitable additives include, for example, dissolved salts with cationsselected from the group consisting of ammonium, d-block metal cations(hafnium, zirconium, lanthanum, or the like), f-block metal cations(cerium, lutetium or the like), p-block metal cations (aluminum, tin, orthe like), alkali metals (lithium, sodium, potassium or the like), andcombinations thereof, and with anions selected from the group consistingof fluoride, chloride, bromide, iodide, nitrate, sulfate, phosphate,silicate, borate, peroxide, butoxide, formate, oxalate,ethylenediamine-tetraacetic acid (EDTA), tungstate, molybdate, or thelike and combinations thereof. Other potentially useful additivesinclude, for example, molecular chelating agents, such as polyamines,alcohol amines, amino acids, carboxylic acids, or combinations thereof.If the optional additives are present, the developer can comprise nomore than about 10 weight percent additive and in further embodiments nomore than about 5 weight percent additive. A person of ordinary skill inthe art will recognize that additional ranges of additive concentrationswithin the explicit ranges above are contemplated and are within thepresent disclosure. The additives can be selected to improve contrast,sensitivity and line width roughness. The additives in the developer canalso inhibit formation and precipitation of metal oxide particles.

With a weaker developer, e.g., lower concentration aqueous developer,diluted organic developer or compositions in which the coating has alower development rate, a higher temperature development process can beused to increase the rate of the process. With a stronger developer, thetemperature of the development process can be lower to reduce the rateand/or control the kinetics of the development. In general, thetemperature of the development can be adjusted between the appropriatevalues consistent with the volatility of the solvents. Additionally,developer with dissolved coating material near the developer-coatinginterface can be dispersed with ultrasonication during development.

The developer can be applied to the patterned coating material using anyreasonable approach. For example, the developer can be sprayed onto thepatterned coating material. Also, spin coating can be used. Forautomated processing, a puddle method can be used involving the pouringof the developer onto the coating material in a stationary format. Ifdesired spin rinsing and/or drying can be used to complete thedevelopment process. Suitable rinsing solutions include, for example,ultrapure water, methyl alcohol, ethyl alcohol, propyl alcohol andcombinations thereof for negative patterning and ultrapure water forpositive patterning. After the image is developed, the coating materialis disposed on the substrate as a pattern.

After completion of the development step, the coating materials can beheat treated to further condense the material and to further dehydrate,densify, or remove residual developer from the material. This heattreatment can be particularly desirable for embodiments in which theoxide coating material is incorporated into the ultimate device,although it may be desirable to perform the heat treatment for someembodiments in which the coating material is used as a resist andultimately removed if the stabilization of the coating material isdesirable to facilitate further patterning. In particular, the bake ofthe patterned coating material can be performed under conditions inwhich the patterned coating material exhibits desired levels of etchselectivity. In some embodiments, the patterned coating material can beheated to a temperature from about 100° C. to about 600° C., in furtherembodiments from about 175° C. to about 500° C. and in additionalembodiments from about 200° C. to about 400° C. The heating can beperformed for at least about 1 minute, in other embodiment for about 2minutes to about 1 hour, in further embodiments from about 2.5 minutesto about 25 minutes. The heating may be performed in air, vacuum, or aninert gas ambient, such as Ar or N₂. A person of ordinary skill in theart will recognize that additional ranges of temperatures and time forthe heat treatment within the explicit ranges above are contemplated andare within the present disclosure. Likewise, non-thermal treatments,including blanket UV exposure, or exposure to an oxidizing plasma suchas 02 may also be employed for similar purposes.

With conventional organic resists, structures are susceptible to patterncollapse if the aspect ratio, height divided by width, of a structurebecomes too large. Pattern collapse can be associated with mechanicalinstability of a high aspect ratio structure such that forces, e.g.,surface tension, associated with the processing steps distort thestructural elements. Low aspect ratio structures are more stable withrespect to potential distorting forces. With the patternable coatingmaterials described herein, due to their high etch resistance and theability to process effectively the structures with thinner layers ofcoating material, improved patterning can be accomplished without theneed for high aspect ratio patterned coating material. Thus, very highresolution features have been formed without resorting to high aspectratio features in the patterned coating material.

The resulting structures can have sharp edges with very low line-widthroughness. In particular, in addition to the ability to reduceline-width roughness, the high contrast also allows for the formation ofsmall features and spaces between features as well as the ability toform very well resolved two-dimensional patterns (e.g., sharp corners).Thus, in some embodiments, adjacent linear segments of neighboringstructures can have an average pitch (half-pitch) of no more than about60 nm (30 nm half-pitch), in some embodiments no more than about 50 nm(25 nm half-pitch) and in further embodiments no more than about 34 nm(17 nm half-pitch). Pitch can be evaluated by design and confirmed withscanning electron microscopy (SEM), such as with a top-down image. Asused herein, pitch refers to the spatial period, or the center-to-centerdistances of repeating structural elements, and as generally used in theart a half-pitch is a half of the pitch. Feature dimensions of a patterncan also be described with respect to the average width of the feature,which is generally evaluated away from corners or the like. Also,features can refer to gaps between material elements and/or to materialelements. In some embodiments, average widths can be no more than about25 nm, in further embodiments no more than about 20 nm, and inadditional embodiments no more than about 15 nm. Average line-widthroughness can be no more than about 5 nm, in some embodiments no morethan about 4.5 nm and in further embodiments from about 2.5 nm to about4 nm. Evaluating line-width roughness is performed by analysis oftop-down SEM images to derive a 3σ deviation from the mean line-width.The mean contains both high-frequency and low-frequency roughness, i.e.,short correlation lengths and long correlation lengths, respectively.The line-width roughness of organic resists is characterized primarilyby long correlation lengths, while the present organometallic coatingmaterials exhibit significantly shorter correlation lengths. In apattern transfer process, short correlation roughness can be smoothedduring the etching process, producing a much higher fidelity pattern. Aperson of ordinary skill in the art will recognize that additionalranges of pitch, average widths and line-width roughness within theexplicit ranges above are contemplated and are within the presentdisclosure. Based on these processes, the patterning can be adapted tothe formation of various devices such as electronic integrated circuits,generally through the repeated patterning process to form appropriatelylayered structures, such as transistors or other components.

Wafer throughput is a substantially limiting factor for implementationof EUV lithography in high-volume semiconductor manufacturing, and isdirectly related to the dose required to pattern a given feature.However, while chemical strategies exist to reduce imaging dose, anegative correlation between the imaging dose required to print a targetfeature, and feature size uniformity (such as LWR) is commonly observedfor EUV photoresists at feature sizes and pitches<50 nm, therebylimiting final device operability and wafer yields. However, theprecursors, precursor solutions, and photoresist film described hereinhave been found avoid this limitation and enable reduced EUV imagingdose without concomitant increase in LWR over a substantial dose range.By utilizing precursor solutions comprising blends of R_(n)SnX_((4-n))and SnX₄ hydrolyzed in-situ during coating and bake steps as detailed inthe following examples, a dose reduction of >30% with equivalent orlower LWR is observed relative to photoresist films derived from amixture of pre-hydrolyzed organotin oxide hydroxide compounds (preparedas described in the '839 application) when processed under similarconditions.

Based on the improved process described in the Examples below, theimproved properties of the coating material can be correspondinglycharacterized. For example, a substrate comprising an inorganicsemiconductor layer and a radiation sensitive coating material along asurface can be subjected to patterning with EUV light at a wavelength of13.5 nm in a pattern of 16-nm lines on a 32-nm pitch. To evaluate thecoating material the dose to achieve a critical dimension of 16 nm canbe evaluated along with the achievable line width roughness (LWR). Theimproved coatings can achieve a critical dimension of 16 nm with a dosefrom about 8 mJ/cm2 to about 25 mJ/cm2 with a line width roughness of nomore than about 4 nm. SuMMIT analysis software (EUV TechnologyCorporation) was used to extract resist critical dimension (CD) andline-width-roughness (LWR) from SEM images.

In further embodiments, the improved patterning capability can beexpressed in terms of the dose-to-gel value. A structure comprising asubstrate and a radiation sensitive coating comprising an alkyl metaloxide hydroxide can have a dose-to-gel (D_(g)) of no more than about6.125 mJ/cm² and in further embodiments from about 5.5 mJ/cm² to about 6mJ/cm². Evaluation of dose-to-gel is explained in the Examples below.

REFERENCES (INCORPORATED HEREIN BY REFERENCE)

-   1) Maeng, W. J.; Pak, S. J.; Kim, H. J. Vac. Sci. Tech B. 2006, 24,    2276.-   2) Rodriguez-Reyes, J. C. F.; Teplyakov, A. V. J. Appl. Phys. 2008,    104, 084907.-   3) Leskelä, M.; Ritala, M. Thin Solid Films 2002, 409, 138.-   4) Leskelä, M.; Ritala, M. J. Phys. IV 1999, 9, Pr8-852.-   5) Atagi, L. M.; Hoffman, D. M.; Liu, J. R.; Zheng, Z.; Chu, W. K.;    Rubiano, R. R.; Springer, R. W.; Smith, D. C. Chem. Mater. 1994, 6,    360.

EXAMPLES Example 1—Preparation of Precursors for In Situ Hydrolysis

This example is directed to the formation of organotin amido compoundsthat are suitable for in situ hydrolysis to form coatings of organotinoxide hydroxides.

The precursor, tert-butyl tris(diethylamido)tin, (tBuSn(NEt₂)₃,hereinafter P-1) was synthesized after the method reported in Hänssgen,D.; Puff, H.; Beckerman, N. J. Organomet. Chem. 1985, 293, 191,incorporated herein by reference. Tetrakis(diethylamido)tin and tBuLireagents were purchased from Sigma-Aldrich and used without furtherpurification. Reagents were reacted in stoichiometric quantities at −78°C. in anhydrous hexanes (Sigma-Aldrich). Precipitated lithium amidesalts were removed via filtration and the product rinsed with hexanes,and the solvent stripped under vacuum. The crude product was distilledunder vacuum (˜0.3 torr at 95° C.).

A solution was prepared in an Ar-filled glove box by weighing 1.177 g(3.0 mmol) of P-1 in a 30-mL amber glass vial and then adding 15 mL ofanhydrous 4-methyl-2-pentanol (dried 24 h over 3A molecular sieves). Thevial was capped and agitated. This stock solution was diluted 1 part in2.85 parts (volume) anhydrous 4-methyl-2-pentanol prior to coating.

The precursor, isopropyl tris(dimethylamido)tin, (iPrSn(NMe₂)₃,hereinafter P-2) was synthesized under inert atmosphere and subsequentlydissolved in toluene to form a resist precursor solution. Under argon, a1-L Schlenk-adapted round bottom flask was charged with LiNMe₂ (81.75 g,1.6 mol, Sigma-Aldrich) and anhydrous hexanes (700 mL, Sigma-Aldrich) toform a slurry. A large stir bar was added and the vessel sealed. Anaddition funnel under positive argon pressure was charged with iPrSnCl₃(134.3 g, 0.5 mol, Gelest) via syringe and then attached to the reactionflask. The reaction flask was cooled to −78° C. and the iPrSnCl₃ wasthen added dropwise over a period of 2 hours. The reaction was warmed toroom temperature overnight while stirring. The reaction produces aby-product solid. After settling, the solid was filtered under positiveargon pressure through an in-line cannula filter. The solvent was thenremoved under vacuum, and the residue distilled under reduced pressure(50-52° C., 1.4 mmHg) to give a pale yellow liquid (110 g, 75% yield).¹H and ¹¹⁹Sn NMR spectra of the distillate in a C₆D₆ solvent werecollected on a Bruker DPX-400 (400 MHz, BBO probe) spectrometer.Observed ¹H resonances (s, 2.82 ppm, —N(CH₃)₂; d 1.26 ppm, —CH₃; m, 1.60ppm, —CH) match the predicted spectrum for iPrSn(NMe₂)₃. The primary¹¹⁹Sn resonance at −65.4 ppm is consistent with a major product having asingle tin environment; the chemical shift is comparable to reportedmonoalkyl tris(dialkylamido)tin compounds.

A solution was prepared in an Ar-filled glove box by weighing 0.662 g(2.25 mmol) of P-2 in a 30 mL amber glass vial. A 15-mL volume ofanhydrous toluene (dried 24 h over 3A molecular sieves) were then addedto make a stock solution (SOL-2). The vial was then capped and agitated.This stock solution was diluted 1 part in 3 parts (volume) anhydroustoluene prior to coating.

Example 2—Patterning of In Situ Hydrolysed Photoresist Coatings

This example demonstrates the successful in situ hydrolysis of coatingsformed from the compositions of Example 1 and the subsequent EUVpatterning.

Thin films were deposited on silicon wafers (100-mm diameter) with anative-oxide surface. The Si wafers were treated with ahexamethyldisilazane (HMDS) vapor prime prior to deposition of the amidoprecursor. Solutions of P-1 in 4-methyl-2-pentanol were spin-coated onsubstrates in air at 1500 rpm and baked on a hotplate in air for 2 minat 100° C. to evaporate residual solvent and volatile hydrolysisproducts. Film thickness following coating and baking was measured viaellipsometry to be ˜31 nm.

The coated substrates were exposed to extreme ultraviolet radiation(Lawrence Berkeley National Laboratory Micro Exposure Tool). A patternof 17-nm lines on a 34-nm pitch was projected onto the wafer using13.5-nm wavelength radiation, dipole illumination, and a numericalaperture of 0.3. The patterned resists and substrates were thensubjected to a post-exposure bake (PEB) on a hotplate for 2 min at 170°C. in air. The exposed film was then dipped in 2-heptanone for 15seconds, then rinsed an additional 15 seconds with the same developer toform a negative tone image, i.e., unexposed portions of the coating wereremoved. A final 5-min hotplate bake at 150° C. in air was performedafter development. FIG. 7 exhibits an SEM image of 16.7-nm resist linesproduced from P-1 cast from 4-methyl-2-pentanol on a 34-nm pitch at aEUV dose of 56 mJ/cm² with a calculated LWR of 2.6 nm.

A second film was cast from the solution of P-2 in toluene usingidentical coating and bake conditions as above. A linear array of 50circular pads ˜500 um in diameter were projected on the wafer using EUVlight. Pad exposure times were modulated to step the delivered EUV dosefor each pad from 1.38 to 37.99 mJ cm⁻² with an exponential 7% step.Following the PEB, development, and final bake processes describedabove, a J. A. Woollam M-2000 Spectroscopic ellipsometer was used tomeasure the residual thickness of the exposed pads. The thickness ofeach pad is plotted as a function of delivered EUV dose in FIG. 8. Theresulting curve clearly illustrates the negative tone contrast generatedon exposure, as residual film thickness starts at ˜0 and reaches amaximum (dose to gel, D_(g)) at approximately 15.8 mJ cm⁻² delivereddose.

Example 3—Evaluation of In Situ Hydrolyzed Coatings

This example provides evidence of the substantially complete hydrolysisthrough the in situ hydrolysis approach for precursors havinghydrolysable bonds to Sn.

For comparison, isopropyl tin oxide hydroxide was prepared for formationof a radiation sensitive coating. A solid hydrolysate of isopropyltintrichloride (iPrSnCl₃, Gelest) was prepared by rapidly adding 6.5 g (24mmol) of isopropyltin trichloride to 150 mL of 0.5-M NaOH (aq) withvigorous stirring, immediately producing a precipitate. The resultingmixture was stirred for 1 h at room temperature and then filtered withsuction through no. 1 filter paper (Whatman). The retained solids werewashed three times with ˜25-mL portions of DI H₂O and then dried for 12h under vacuum (˜5 torr) at room temperature. Elemental analyses (18.04%C, 3.76% H, 1.38% Cl; Microanalysis, Inc.; Wilmington, Del.) of thedried powder, indicated substantial removal of chloride ions uponhydrolysis of isopropyltin trichloride and an approximate hydrolysateempirical formula of ^(i)PrSnO_((3/2-(x/2)))(OH)_(x) where x≈1(hereinafter P-3). (Calculated for C₃H₈O₂Sn: 18.50% C, 4.14% H, 0.00%Cl).

A solution of the solid hydrolysate iPrSnO_((3/2-(x/2)))(OH)_(x was)prepared by dissolving the dried powder in 2-butanone to a total Snconcentration of ˜0.25 M. A solution of P-2 in anhydrous4-methyl-2-pentanol was prepared by adding 1.47 g (5.0 mmol) P-2 to 10mL 4-methyl-2-pentanol as previously described. Thin films were cast byspin coating each solution on a 25 mm×25 mm Si wafer. The solution ofP-2 was coated at 2000 rpm, while the solution of P-3 was coated at 1250rpm. Following coating, each film was baked at 150° C. in air for 2minutes. The alcohol may react with P-2 to form alkoxide ligands, but inany case, if alkoxide ligands form, these seem to be further hydrolysedto form the oxide hydroxide composition.

Fourier Transform Infrared (FTIR) transmission spectra of the two filmswere collected on a Nicolet 6700 spectrometer using a bare substrate asa background. Representative spectra for the two films (FIG. 8) arequalitatively very similar, suggesting substantial hydrolysis andelimination of amido/alkoxo ligands from the solution of P-2 anddeposition of the oxide hydroxide in both cases. In particular, theregions from 2800-3000 cm⁻¹ and 1100-1500 cm⁻¹ are almost identical,indicating a similar CH_(x) composition between the two films, as wellas the absence of substantial C—N species.

Example 4—Preparation of Hydrolysable Precursors withTetrakis-Dialkylamido or -Tert-Butoxo Tin Compounds

This example describes formation of mixed hydrolysable precursorcompounds to provide for control of the stoichiometry of radiationsensitive ligands relative to metal in the radiation sensitive coatings.

Tert-butyl tris(diethylamido)tin was synthesized as described inExample 1. Tetrakis(dimethylamido)tin, (Sn(NMe₂)₄, FW=295.01) waspurchased from Sigma-Aldrich and used without further purification.

Tin (IV) tert-butoxide, (Sn(O^(t)Bu)₄, FW=411.16, hereinafter P-5) wasprepared after the method of Hampden-Smith et al. Canadian Journal ofChemistry, 1991, 69, 121, incorporated herein by reference: Stannouschloride (152 g/0.8 mol) and pentane (1 L) were added to a 3-Loven-dried round-bottom flask equipped with a magnetic stir-bar andpurged with nitrogen. A 1-L pressure-equalizing addition funnel fittedwith a nitrogen pressure inlet was charged with diethylamine (402 mL/3.9mol) and pentane (600 mL) and then attached to the flask, and the flasksubmerged in an ice bath. The amine solution was then added dropwisesuch that a gentle reflux was maintained. Upon completion of the amineaddition, 2-methyl-2-propanol (290 g/3.9 mol) in pentane (50 mL) wasadded to the addition funnel and thence dropwise to the flask. Afterstirring for 18 hours, the slurry was transferred into an air-freefritted filter flask and precipitated salts removed. The solvent wasremoved under reduced pressure and the target compound distilled(B.P.=60-62 C @ 1 torr). ¹H NMR (C₆D₆): 1.45 ppm (s); ¹¹⁹Sn NMR (C₆D₆):−371.4 ppm (s).

Stock solutions of P-1 (^(t)BuSn(NEt₂)₃, hereinafter S-1), P-4(Sn(NMe₂)₄, hereinafter S-2), and P-5 (Sn(O^(t)Bu)₄, hereinafter S-3)were prepared by transferring each of the corresponding compounds viacannula into separate flasks containing anhydrous 4-methyl-2-pentanol(dried 24 h over 4A molecular sieves). Additional dry4-methyl-2-pentanol was then added to dilute the solutions to 0.25 M(Sn) final concentration.

A further stock solution, S-4, was prepared by cannulating 41 g of P-1into a round bottom flask immersed in an iso-propanol/dry ice bath andcontaining 250 mL of methanol while stirring on a magnetic stir plate.After the transfer of the ^(t)BuSn(NEt₂)₃ aliquot, the flask containingthe mixture was removed from the ice bath and allowed to reach roomtemperature. Next, the flask containing the mixture was brought to 50°C. in a water bath attached to a rotary evaporator and the solventstripped at reduced pressure (10 mtorr) until solvent evaporation wassubstantially complete and a viscous yellow oil obtained. Finally, theyellow oil was dissolved in 1.0 L of 4-methy-2-pentanol. The resultingsolution was determined to have a molarity of 0.097 M [Sn] based on theresidual mass of the solution following solvent evaporation andsubsequent thermal decomposition of the residual solids to SnO₂.

Precursor coating solutions CS-a, CS-b, and CS-c were prepared by mixingstock solution S-1 with S-2 in 0, 5:1, and 9:1 volume ratios to producecoating solutions where 0 (a), 10 (b), and 20 (c) mol % of the total Snconcentration in the mixture was derived from Sn(NMe₂)₄. These solutionswere then further diluted with 4-methyl-2-pentanol to 0.070 M (total Sn)prior to spin coating. For example, to prepare 200 mL of CS-b, 5.6 mL ofthe stock solution prepared from Sn(NMe₂)₄ (S-2) was added to 50.4 mL ofthe solution prepared from ^(t)BuSn(NEt₂)₃ (S-1), mixed vigorously, anddiluted to 200 mL total volume with dry 4-methyl-2-pentanol. A summaryof precursor coating solutions, concentrations, and compositions ispresented in Table 2.

Precursor coating solutions CS-e-h were prepared with a total Snconcentration of 0.044 M by mixing stock solution S-4 with stocksolutions S-2 and S-3 in appropriate volume ratios such that 10 and 20mol % of the total Sn concentration was derived from Sn(NMe₂)₄ (CS-e,CS-f, respectively), and Sn(O^(t)Bu)₄ (CS-g, CS-h) and diluting with dry4-methyl-2-pentanol. Precursor coating solution CS-d was prepared bydirectly diluting stock solution S-4 with dry 4-methyl-2-pentanol to afinal concentration of 0.042 M Sn. As an example, 200 mL of precursorcoating solution CS-e is prepared by mixing 72.6 mL of S-4 with 7.04 mLof S-3, and diluting to 200 mL total volume with dry4-methyl-2-pentanol.

TABLE 2 Precursor ^(t)Bu—Sn Total Conc. mol % Sn mol % Sn Coating Stock[Sn] from from Solution Solution (M) Sn(NMe)₄ Sn(O^(t)Bu)₄ a 1 0.070 0 0b 1 0.070 10 0 c 1 0.070 20 0 d 4 0.042 0 0 e 4 0.044 10 0 f 4 0.044 200 g 4 0.044 0 10 h 4 0.044 0 20

Precursor coating solution CS-i was prepared by mixing a methanolsolution containing a pre-hydrolysed t-butyl tin oxide hydroxidehydrolysate with a 4-methyl-2-pentanol solution of a prehydrolysedi-propyl tin oxide hydroxide hydrolysate, and diluting the resultingmixture to 0.03 M [Sn] with pure solvents as described in the '839application. The resulting solutions are characterized as a blend of^(i)PrSnO_((3/2-(x/2)))(OH)_(x) and ^(t)BuSnO_((3/2-(x/2)))(OH)_(x)hydrolysates, where the fraction of t-BuSnO_((3/2-(x/2)))(OH)_(x) is 40%relative to the total moles of Sn.

Example 5—Patterning with Engineered Coatings with Selected Degree ofRadiation Sensitive Ligands

This example presents results obtain by patterning of coatings formedwith the coating solutions prepared as described in Example 4demonstrating improved patterning with lower radiation doses.

Tert-butyltin oxide hydroxide photoresist films were deposited fromprecursor coating solutions from Example 4 prepared from ^(t)BuSn(NEt₂)₃and, for some coating solutions, Sn(NMe₂)₄ or Sn(O^(t)Bu)₄, and thenexposed with EUV radiation. Thin films for EUV contrast curves weredeposited on silicon wafers (100-mm diameter) with a native-oxidesurface. The Si wafers were treated with a hexamethyldisilazane (HMDS)vapor prime prior to deposition. Precursor coating solutions CS-a, CS-b,and CS-c (0.070 M Sn) prepared according to specification in Table 1from ^(t)BuSn(NEt₂)₃ and 0, 10, and 20 mol % Sn(NMe₂)₄ were spin-coatedthe Si substrates in air at 1500 rpm and baked on a hotplate in air for2 min at 100° C. to eliminate residual solvent and volatile hydrolysisproducts. Film thicknesses following coating and baking were measuredvia ellipsometry to be ˜25-28 nm.

A linear array of 50 circular pads ˜500 μm in diameter were exposed oneach wafer with EUV light using the Lawrence Berkeley NationalLaboratory Micro Exposure Tool. Pad exposure times were modulated tostep the delivered EUV dose for each pad from 1.38 to 37.99 mJ cm⁻² withan exponential 7% step. After exposure, wafers were subjected to apost-exposure bake (PEB) on a hotplate in air at 170° C. for 2 min. Theexposed film was then dipped in 2-heptanone for 15 seconds and rinsed anadditional 15 seconds with the same developer to form a negative toneimage, i.e., unexposed portions of the coating were removed. A final5-min hotplate bake at 150° C. in air was performed after development. AJ. A. Woollam M-2000 spectroscopic ellipsometer was used to measure theresidual thickness of the exposed pads. The measured thicknesses werenormalized to the maximum measured resist thickness and plotted versusthe logarithm of exposure dose to form characteristic curves for eachresist at a series of post exposure bake temperatures. See FIG. 10. Themaximum slope of the normalized thickness vs log dose curve is definedas the photoresist contrast (γ) and the dose value at which a tangentline drawn through this point equals 1 is defined as the photoresistdose-to-gel, (D_(g)). In this way common parameters used for photoresistcharacterization may be approximated following Mack, C. FundamentalPrinciples of Optical Lithography, John Wiley & Sons, Chichester, U.K;pp 271-272, 2007.

The resulting curves clearly illustrate the negative-tone contrastgenerated on exposure, as residual pad thickness for each resist filmstarts at ˜0 and reaches a maximum near D_(g). The dose required toinitiate the development rate change is clearly observed to decrease asthe mol fraction of Sn in the precursor coating solutions correspondingto Sn(NMe₂)₄ is increased from 0 (D_(g)=13.8 mJ cm⁻²), to 10%(D_(g)=10.6 mJ cm⁻²), and finally 20% (D_(g)=5.8 mJ cm⁻²).

High-resolution line-space patterns were likewise printed using a EUVscanner and tert-butyltin oxide hydroxide photoresist films cast fromprecursor coating solutions CS-d, CS-e, and CS-f. Silicon wafers (300-mmdiameter) with a native-oxide surface were used as substrates withoutadditional surface treatment. Precursor coating solutions CS-d-hprepared from ^(t)BuSn(NEt₂)₃ and 0, 10, or 20 mol % Sn(NMe₂)₄ orSn(O^(t)Bu)₄ as described above, as well as CS-i, were spin-coated onthe Si substrates in air at 1000 or 1500 rpm (CS-d only) and baked on ahotplate in air for 2 min at 100° C.

The coated substrates were exposed to extreme ultraviolet radiationusing a NXE:3300B EUV scanner with dipole 60× illumination and anumerical aperture of 0.33. A pattern of 16-nm lines on a 32-nm pitchwas projected on the coated wafer following 2 minute, 100° C. post-applybake (PAB). The exposed resist films and substrates were then subjectedto a PEB on a hotplate for 2 min at 170° C. in air. The exposed filmswere then developed in 2-heptanone for 15 seconds, then rinsed anadditional 15 seconds with the same developer to form a negative toneimage, i.e., unexposed portions of the coating were removed. A final5-min hotplate bake at 150° C. in air was performed after development.FIG. 11 exhibits SEM images of the resulting resist lines developed fromtert-butyltin oxide hydroxide photoresist films. The imaging dose,critical dimension, and line-width roughness are shown for each filmcast from precursor coating solutions prepared from ^(t)BuSn(NEt₂)₃(CS-d), and 10 or 20 mol % Sn(NMe₂)₄ (CS-e, CS-f, respectively), orSn(O^(t)Bu)₄ (CS-g, CS-h). Again, imaging dose is observed to decreasewith increasing fraction of SnX₄ added to the precursor coatingsolution. The imaging dose required to achieve a critical dimension of16 nm is plotted versus the calculated LWR each film cast from precursorcoating solutions d-i is plotted in FIG. 12. Significantly, a>30%reduction in the required imaging dose in is obtained for the films castfrom CS-e and -f, relative to -i without a concomitant increase inline-width-roughness (LWR), indicating a substantial improvement overthe pre-hydrolysed mixed alkyl ligand formulation and an importantcircumvention (over that dose range) of the commonly observed inverserelationship between patterning dose and LWR.

Example 6

Pattering performance is evaluated for coatings prepared with a mixtureof tert-butyl and methyl radiation sensitive ligands.

Specifically, precursor solution preparation, film coating, andlithographic performance were examined in the context of organotin oxidehydroxide photoresist films comprising a mixture of^(t)BuSnO_((3/2-(x/2)))(OH)_(x) and MeSnO_((3/2-(x/2)))(OH)_(x) preparedvia in situ hydrolysis of a precursor solution comprising ^(t)BuSnX₃ andMeSnX₃ compounds.

MeSn(O^(t)Bu)₃ (FW=353.1, hereinafter P-6) was synthesized as followsfrom MeSnCl₃ (Gelest), an oven-dried RBF equipped with an additionfunnel and magnetic stir-bar was charged with 0.8 M MeSnCl₃ in pentane.While cooling with an ice bath, 4 molar equivalents of diethylamine inpentane (5.5 M) were added dropwise through the addition funnel. Uponcomplete addition, 4 molar equivalents of tert-butyl alcohol mixed3.25:1 (vol) in pentane were added, and the solution is allowed to stirat room temperature for 30 min. The reaction mixture was then filteredand volatiles removed under vacuum leaving a product as a light oil. Theproduct was then distilled at 55-60° C. at ˜0.1 torr.

A stock solution of P-6 was prepared by dissolution in dry4-methyl-2-pentanol. This solution of MeSn(O^(t)Bu)₃ was mixed atvarious volume ratios with a second stock solution of prepared from^(t)BuSn(NEt₂)₃ in 4-methyl-2-pentanol in an identical manner tosolution S-4 above and diluted with the same solvent to achieve a totalSn concentration of 0.05 M. By this method a series of precursorsolutions were prepared with a range of 0-60 mol % of the total alkyl-Snconcentration added as MeSn(OtBu)₃. These precursor solutions werecoated on 100-mm Si substrates, baked at 100° C., and then exposed toEUV radiation at varying doses creating a contrast array as previouslydescribed.

Following exposure the coated wafers were baked at 170° C. in air anddeveloped for 15 s in 2-heptanone, rinsed for 15 s with a wash-bottlecontaining the same solvent, then dried under N₂ and baked in air at150° C. for 5 min. The residual thickness of each exposure pad wasmeasured and plotted as a function of dose in FIG. 13. Extracted resistmetrics (see Example 5) are tabulated in Table 3. It is observed fromFIG. 13 that Dg decreases markedly as the mol % of MeSn(OtBu)₃ in theprecursor solution increases, while the contrast remains high, even atrelatively low values of D_(g). Importantly, the residual thickness<<D_(g) is consistently near zero, indicating the resist is cleared inthe unexposed region with minimal residue (scum).

TABLE 3 Mol % D_(g) γ MeSn(OtBu)₃ (mJ/cm²) Contrast 0 16.1 15.8 10 14.114.8 20 11.6 15.6 40 7.3 12.7 60 2.3 9.4

A pattern of 18-nm lines on a 36-nm pitch was exposed on similarlyprocessed wafers, using the Lawrence Berkeley National Laboratory MicroExposure Tool using 13.5-nm wavelength radiation, dipole illumination,and a numerical aperture of 0.3. The line width (CD) measured with a SEMand plotted versus imaging dose in FIG. 14. Again the imaging doserequired to achieve a given line-width is found to strongly decrease asthe mol-fraction of MeSn(O^(t)Bu)₃ in the precursor solution isincreased. Representative SEM images from the same wafers are shown inFIG. 15 for precursor solutions containing a) 20%, b) 40%, and c) 60%P-6.

The embodiments above are intended to be illustrative and not limiting.Additional embodiments are within the claims and additional inventiveconcepts. In addition, although the present invention has been describedwith reference to particular embodiments, those skilled in the art willrecognize that changes can be made in form and detail without departingfrom the spirit and scope of the invention. Any incorporation byreference of documents above is limited such that no subject matter isincorporated that is contrary to the explicit disclosure herein. To theextent that specific structures, compositions and/or processes aredescribed herein with components, elements, ingredients or otherpartitions, it is to be understand that the disclosure herein covers thespecific embodiments, embodiments comprising the specific components,elements, ingredients, other partitions or combinations thereof as wellas embodiments consisting essentially of such specific components,ingredients or other partitions or combinations thereof that can includeadditional features that do not change the fundamental nature of thesubject matter, as suggested in the discussion, unless otherwisespecifically indicated.

Additional Inventive Concepts

1. A method for forming a radiation patternable coating comprising anoxo-hydroxo network with metal cations having organic ligands with metalcarbon bonds and metal oxygen bonds, the method comprising:

inputting into a deposition chamber closed from the ambient atmosphere afirst precursor vapor comprising a composition represented by theformula R_(n)SnX_(4-n) where n=1 or 2, wherein R is an organic ligandwith 1-31 carbon atoms bound to Sn with a metal-carbon bond, n=1 or 2,and X is a ligand having a hydrolysable bond with Sn and

inputting sequentially or at the same time a second precursor vaporcomprising an oxygen-containing compound capable of reacting with thecomposition in the first precursor vapor under conditions in thedeposition chamber to form a composition with non-volatile componentsand a volatile component comprising a reaction product with X ligand orligands, wherein a substrate is configured with a surface to receive thenon-volatile components of the composition.

2. The method of additional inventive concept 1 wherein the secondprecursor vapor comprises water vapor.3. The method of additional inventive concept 1 wherein the depositionchamber has a pressure from about 0.01 Torr to about 25 Torr.4. The method of additional inventive concept 1 wherein the depositionchamber has a temperature from about 40° C. to about 175° C.5. The method of additional inventive concept 1 further including a stepof inputting an inert purge gas between each cycle of inputtingprecursor vapors.6. The method of additional inventive concept 1 where a third precursoris separately inputted to the chamber the precursor comprising ML_(v),where v is 2≤v≤6 and L is an oxidixable ligand or a ligand having ahydrolysable M-L bond or a combination thereof, and M is a metalselected from groups 2-16 of the periodic table.7. A coated substrate comprising a substrate with a surface and acoating on the surface comprising:

an organometallic composition represented by the formula y(R_(z)SnO_((2-(z/2)-(w/2)))(OH)_(w).z MO_(((m/2)-1/2))(OH)_(l) where Ris a hydrocarbyl group with 1-31 carbon atoms or a combination thereof,0<z≤2, 0<(z+w)≤4, m=formal valence of M^(m+), 0≤1≤m, y/z=(0.05 to 0.6),and M=M′ or Sn, where M′ is a non-tin metal of groups 2-16 of theperiodic table.

8. A structure comprising a substrate and a radiation sensitive coatingcomprising an alkyl metal oxide hydroxide having a dose-to-gel (D_(g))of no more than about 6.125 mJ/cm⁻².9. A structure comprising a substrate comprising an inorganicsemiconductor layer and a radiation sensitive coating material along asurface, wherein the radiation coating material can be patterned withEUV light at a wavelength of 13.5 nm in a pattern of 16-nm lines on a32-nm pitch to achieve a critical dimension of 16 nm with a dose fromabout 8 mJ/cm2 to about 25 mJ/cm2 with a line width roughness of no morethan about 4 nm.10. The structure of additional inventive concept 9 wherein theradiation sensitive coating material has at least 5 weight percent ofmetal.11. The structure of additional inventive concept 9 wherein theradiation sensitive coating material has at least 20 weight percent ofmetal.

What is claimed is:
 1. A method for forming a radiation patternableorganometallic coating, the method comprising: depositing a tincomposition having organic ligands and hydrolysable ligands to form acoating with a dry thickness from about nanometers (nm) to about 50 nm,wherein the organic ligands comprise radiation sensitive Sn—C bonds, andwherein the depositing is by a vapor-based deposition process.
 2. Themethod of claim 1 further comprising at least partially hydrolysing thehydrolysable ligands to form oxo/hydroxo ligands.
 3. The method of claim2 wherein the hydrolysis involves atmospheric water.
 4. The method ofclaim 3 wherein the hydrolysis is performed following deposition of thecoating.
 5. The method of claim 3 wherein the hydrolysis is performedduring deposition of the coating.
 6. The method of claim 1 wherein thevapor-based deposition process is chemical vapor deposition (CVD),physical vapor deposition (PVD), or atomic layer deposition (ALD). 7.The method of claim 1 wherein the coating comprises Sn—O—H and Sn—O—Snbonds and the radiation sensitive Sn—C bonds.
 8. The method of claim 1wherein the organic ligands comprise an alkyl ligand, a branched alkylligand, a cyclic alkyl, an alkenyl ligand, an aryl ligand, heteroatomsubstituted derivatives thereof, or a combination thereof, each ligandcontaining 1 to 31 carbon atoms.
 9. The method of claim 8 wherein theorganic ligands comprise a ligand substituted with cyano, thio, silyl,ether, keto, ester, or halogenated groups, or combinations thereof. 10.The method of claim 1 wherein the organic ligands comprise methyl,ethyl, propyl, isopropyl, butyl, sec-butyl, t-butyl, t-amyl, cyclohexyl,cyclopentyl, cyclobutyl, cyclopropyl, 1-adamantyl, 2-adamantyl, phenyl,benzyl, allyl, or combinations thereof.
 11. The method of claim 1wherein the tin composition comprises at least one branched alkylligand.
 12. The method of claim 1 wherein the tin composition comprisesone or more compositions with different organic ligands in a blend. 13.The method of claim 1 wherein the tin composition comprises a blend ofdifferent organic ligands, different hydrolysable ligands, or acombination thereof.
 14. The method of claim 1 wherein the tincomposition comprises a combination of two or more differenthydrolysable ligands.
 15. The method of claim 1 wherein the hydrolysableligands comprise a halide, an alkoxide, an alkylamide, an alkylnide, anazide, a dialkylamide, a siloxide, a silylamide, disilylamide, anaryloxide, an amidato, an amidinato, an imido, fluorinated analoguesthereof, or a mixture thereof.
 16. The method of claim 1 wherein the tincomposition comprises t-butyl tris(dimethylamido) tin, i-propyl(dimethylamido) tin, t-butyl tris(diethylamido)tin, i-propyl tintrichloride, or combinations thereof.
 17. The method of claim 1 whereinthe coating has a thickness variation of no more than 50% from theaverage at any point along the coating as measurable by ellipsometryand/or x-ray reflectivity.
 18. The method of claim 1 further comprisingheating the deposited tin composition to temperatures from about 45° C.to about 250° C. for 0.1 minute to 30 minutes to form the radiationpatternable organometallic coating.
 19. The method of claim 1 whereinthe depositing is onto a substrate comprising a silicon wafer.
 20. Themethod of claim 1 further comprising irradiating the radiationpatternable organometallic coating using patterned radiation to form alatent image.
 21. The method of claim 20 wherein the irradiatingcomprises EUV, UV, or e-beam radiation exposure.
 22. The method of claim20 wherein the irradiating causes a reaction in the exposed portion ofthe latent image, the reaction comprising condensing of the tincomposition and cleaving of Sn—C bonds.
 23. The method of claim 22wherein the exposed portion of the latent image is not soluble inorganic solvents.
 24. The method of claim 20 wherein the irradiatingcomprises EUV radiation at a dose from 3 mJ/cm⁻² to 150 mJ/cm⁻².
 25. Themethod of claim 20 further comprising a developing step after theirradiating step.
 26. The method of claim 1 wherein the tin compositionfurther comprises a blend of one or more non-tin metals.
 27. A methodfor forming a radiation patternable organometallic coating, the methodcomprising: depositing a tin composition having organic ligands andhydrolysable ligands to form a coating with a dry thickness from 1nanometers (nm) to 50 nm, wherein the organic ligands comprise radiationsensitive Sn—C bonds, and wherein the hydrolysable ligands comprise analkoxide, an alkylamide, an alkylnide, an azide, a dialkylamide, asiloxide, a silylamide, disilylamide, an aryloxide, an amidato, anamidinato, an imido, fluorinated analogues thereof, or a mixturethereof.
 28. The method of claim 27 wherein the tin compositioncomprises a blend of different organic ligands, different hydrolysableligands, or a combination thereof.
 29. The method of claim 27 whereinthe tin composition comprises at least one branched alkyl ligand.